diff options
Diffstat (limited to 'kernel/locking/lockdep.c')
| -rw-r--r-- | kernel/locking/lockdep.c | 6595 |
1 files changed, 6595 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c new file mode 100644 index 000000000..3b38303ed --- /dev/null +++ b/kernel/locking/lockdep.c @@ -0,0 +1,6595 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * kernel/lockdep.c + * + * Runtime locking correctness validator + * + * Started by Ingo Molnar: + * + * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra + * + * this code maps all the lock dependencies as they occur in a live kernel + * and will warn about the following classes of locking bugs: + * + * - lock inversion scenarios + * - circular lock dependencies + * - hardirq/softirq safe/unsafe locking bugs + * + * Bugs are reported even if the current locking scenario does not cause + * any deadlock at this point. + * + * I.e. if anytime in the past two locks were taken in a different order, + * even if it happened for another task, even if those were different + * locks (but of the same class as this lock), this code will detect it. + * + * Thanks to Arjan van de Ven for coming up with the initial idea of + * mapping lock dependencies runtime. + */ +#define DISABLE_BRANCH_PROFILING +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/sched/clock.h> +#include <linux/sched/task.h> +#include <linux/sched/mm.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/proc_fs.h> +#include <linux/seq_file.h> +#include <linux/spinlock.h> +#include <linux/kallsyms.h> +#include <linux/interrupt.h> +#include <linux/stacktrace.h> +#include <linux/debug_locks.h> +#include <linux/irqflags.h> +#include <linux/utsname.h> +#include <linux/hash.h> +#include <linux/ftrace.h> +#include <linux/stringify.h> +#include <linux/bitmap.h> +#include <linux/bitops.h> +#include <linux/gfp.h> +#include <linux/random.h> +#include <linux/jhash.h> +#include <linux/nmi.h> +#include <linux/rcupdate.h> +#include <linux/kprobes.h> +#include <linux/lockdep.h> +#include <linux/context_tracking.h> + +#include <asm/sections.h> + +#include "lockdep_internals.h" + +#include <trace/events/lock.h> + +#ifdef CONFIG_PROVE_LOCKING +static int prove_locking = 1; +module_param(prove_locking, int, 0644); +#else +#define prove_locking 0 +#endif + +#ifdef CONFIG_LOCK_STAT +static int lock_stat = 1; +module_param(lock_stat, int, 0644); +#else +#define lock_stat 0 +#endif + +#ifdef CONFIG_SYSCTL +static struct ctl_table kern_lockdep_table[] = { +#ifdef CONFIG_PROVE_LOCKING + { + .procname = "prove_locking", + .data = &prove_locking, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, +#endif /* CONFIG_PROVE_LOCKING */ +#ifdef CONFIG_LOCK_STAT + { + .procname = "lock_stat", + .data = &lock_stat, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, +#endif /* CONFIG_LOCK_STAT */ + { } +}; + +static __init int kernel_lockdep_sysctls_init(void) +{ + register_sysctl_init("kernel", kern_lockdep_table); + return 0; +} +late_initcall(kernel_lockdep_sysctls_init); +#endif /* CONFIG_SYSCTL */ + +DEFINE_PER_CPU(unsigned int, lockdep_recursion); +EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion); + +static __always_inline bool lockdep_enabled(void) +{ + if (!debug_locks) + return false; + + if (this_cpu_read(lockdep_recursion)) + return false; + + if (current->lockdep_recursion) + return false; + + return true; +} + +/* + * lockdep_lock: protects the lockdep graph, the hashes and the + * class/list/hash allocators. + * + * This is one of the rare exceptions where it's justified + * to use a raw spinlock - we really dont want the spinlock + * code to recurse back into the lockdep code... + */ +static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; +static struct task_struct *__owner; + +static inline void lockdep_lock(void) +{ + DEBUG_LOCKS_WARN_ON(!irqs_disabled()); + + __this_cpu_inc(lockdep_recursion); + arch_spin_lock(&__lock); + __owner = current; +} + +static inline void lockdep_unlock(void) +{ + DEBUG_LOCKS_WARN_ON(!irqs_disabled()); + + if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current)) + return; + + __owner = NULL; + arch_spin_unlock(&__lock); + __this_cpu_dec(lockdep_recursion); +} + +static inline bool lockdep_assert_locked(void) +{ + return DEBUG_LOCKS_WARN_ON(__owner != current); +} + +static struct task_struct *lockdep_selftest_task_struct; + + +static int graph_lock(void) +{ + lockdep_lock(); + /* + * Make sure that if another CPU detected a bug while + * walking the graph we dont change it (while the other + * CPU is busy printing out stuff with the graph lock + * dropped already) + */ + if (!debug_locks) { + lockdep_unlock(); + return 0; + } + return 1; +} + +static inline void graph_unlock(void) +{ + lockdep_unlock(); +} + +/* + * Turn lock debugging off and return with 0 if it was off already, + * and also release the graph lock: + */ +static inline int debug_locks_off_graph_unlock(void) +{ + int ret = debug_locks_off(); + + lockdep_unlock(); + + return ret; +} + +unsigned long nr_list_entries; +static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES]; +static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES); + +/* + * All data structures here are protected by the global debug_lock. + * + * nr_lock_classes is the number of elements of lock_classes[] that is + * in use. + */ +#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1) +#define KEYHASH_SIZE (1UL << KEYHASH_BITS) +static struct hlist_head lock_keys_hash[KEYHASH_SIZE]; +unsigned long nr_lock_classes; +unsigned long nr_zapped_classes; +unsigned long max_lock_class_idx; +struct lock_class lock_classes[MAX_LOCKDEP_KEYS]; +DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS); + +static inline struct lock_class *hlock_class(struct held_lock *hlock) +{ + unsigned int class_idx = hlock->class_idx; + + /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */ + barrier(); + + if (!test_bit(class_idx, lock_classes_in_use)) { + /* + * Someone passed in garbage, we give up. + */ + DEBUG_LOCKS_WARN_ON(1); + return NULL; + } + + /* + * At this point, if the passed hlock->class_idx is still garbage, + * we just have to live with it + */ + return lock_classes + class_idx; +} + +#ifdef CONFIG_LOCK_STAT +static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats); + +static inline u64 lockstat_clock(void) +{ + return local_clock(); +} + +static int lock_point(unsigned long points[], unsigned long ip) +{ + int i; + + for (i = 0; i < LOCKSTAT_POINTS; i++) { + if (points[i] == 0) { + points[i] = ip; + break; + } + if (points[i] == ip) + break; + } + + return i; +} + +static void lock_time_inc(struct lock_time *lt, u64 time) +{ + if (time > lt->max) + lt->max = time; + + if (time < lt->min || !lt->nr) + lt->min = time; + + lt->total += time; + lt->nr++; +} + +static inline void lock_time_add(struct lock_time *src, struct lock_time *dst) +{ + if (!src->nr) + return; + + if (src->max > dst->max) + dst->max = src->max; + + if (src->min < dst->min || !dst->nr) + dst->min = src->min; + + dst->total += src->total; + dst->nr += src->nr; +} + +struct lock_class_stats lock_stats(struct lock_class *class) +{ + struct lock_class_stats stats; + int cpu, i; + + memset(&stats, 0, sizeof(struct lock_class_stats)); + for_each_possible_cpu(cpu) { + struct lock_class_stats *pcs = + &per_cpu(cpu_lock_stats, cpu)[class - lock_classes]; + + for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++) + stats.contention_point[i] += pcs->contention_point[i]; + + for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++) + stats.contending_point[i] += pcs->contending_point[i]; + + lock_time_add(&pcs->read_waittime, &stats.read_waittime); + lock_time_add(&pcs->write_waittime, &stats.write_waittime); + + lock_time_add(&pcs->read_holdtime, &stats.read_holdtime); + lock_time_add(&pcs->write_holdtime, &stats.write_holdtime); + + for (i = 0; i < ARRAY_SIZE(stats.bounces); i++) + stats.bounces[i] += pcs->bounces[i]; + } + + return stats; +} + +void clear_lock_stats(struct lock_class *class) +{ + int cpu; + + for_each_possible_cpu(cpu) { + struct lock_class_stats *cpu_stats = + &per_cpu(cpu_lock_stats, cpu)[class - lock_classes]; + + memset(cpu_stats, 0, sizeof(struct lock_class_stats)); + } + memset(class->contention_point, 0, sizeof(class->contention_point)); + memset(class->contending_point, 0, sizeof(class->contending_point)); +} + +static struct lock_class_stats *get_lock_stats(struct lock_class *class) +{ + return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes]; +} + +static void lock_release_holdtime(struct held_lock *hlock) +{ + struct lock_class_stats *stats; + u64 holdtime; + + if (!lock_stat) + return; + + holdtime = lockstat_clock() - hlock->holdtime_stamp; + + stats = get_lock_stats(hlock_class(hlock)); + if (hlock->read) + lock_time_inc(&stats->read_holdtime, holdtime); + else + lock_time_inc(&stats->write_holdtime, holdtime); +} +#else +static inline void lock_release_holdtime(struct held_lock *hlock) +{ +} +#endif + +/* + * We keep a global list of all lock classes. The list is only accessed with + * the lockdep spinlock lock held. free_lock_classes is a list with free + * elements. These elements are linked together by the lock_entry member in + * struct lock_class. + */ +static LIST_HEAD(all_lock_classes); +static LIST_HEAD(free_lock_classes); + +/** + * struct pending_free - information about data structures about to be freed + * @zapped: Head of a list with struct lock_class elements. + * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements + * are about to be freed. + */ +struct pending_free { + struct list_head zapped; + DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS); +}; + +/** + * struct delayed_free - data structures used for delayed freeing + * + * A data structure for delayed freeing of data structures that may be + * accessed by RCU readers at the time these were freed. + * + * @rcu_head: Used to schedule an RCU callback for freeing data structures. + * @index: Index of @pf to which freed data structures are added. + * @scheduled: Whether or not an RCU callback has been scheduled. + * @pf: Array with information about data structures about to be freed. + */ +static struct delayed_free { + struct rcu_head rcu_head; + int index; + int scheduled; + struct pending_free pf[2]; +} delayed_free; + +/* + * The lockdep classes are in a hash-table as well, for fast lookup: + */ +#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1) +#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS) +#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS) +#define classhashentry(key) (classhash_table + __classhashfn((key))) + +static struct hlist_head classhash_table[CLASSHASH_SIZE]; + +/* + * We put the lock dependency chains into a hash-table as well, to cache + * their existence: + */ +#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1) +#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS) +#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS) +#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain))) + +static struct hlist_head chainhash_table[CHAINHASH_SIZE]; + +/* + * the id of held_lock + */ +static inline u16 hlock_id(struct held_lock *hlock) +{ + BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16); + + return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS)); +} + +static inline unsigned int chain_hlock_class_idx(u16 hlock_id) +{ + return hlock_id & (MAX_LOCKDEP_KEYS - 1); +} + +/* + * The hash key of the lock dependency chains is a hash itself too: + * it's a hash of all locks taken up to that lock, including that lock. + * It's a 64-bit hash, because it's important for the keys to be + * unique. + */ +static inline u64 iterate_chain_key(u64 key, u32 idx) +{ + u32 k0 = key, k1 = key >> 32; + + __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */ + + return k0 | (u64)k1 << 32; +} + +void lockdep_init_task(struct task_struct *task) +{ + task->lockdep_depth = 0; /* no locks held yet */ + task->curr_chain_key = INITIAL_CHAIN_KEY; + task->lockdep_recursion = 0; +} + +static __always_inline void lockdep_recursion_inc(void) +{ + __this_cpu_inc(lockdep_recursion); +} + +static __always_inline void lockdep_recursion_finish(void) +{ + if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion))) + __this_cpu_write(lockdep_recursion, 0); +} + +void lockdep_set_selftest_task(struct task_struct *task) +{ + lockdep_selftest_task_struct = task; +} + +/* + * Debugging switches: + */ + +#define VERBOSE 0 +#define VERY_VERBOSE 0 + +#if VERBOSE +# define HARDIRQ_VERBOSE 1 +# define SOFTIRQ_VERBOSE 1 +#else +# define HARDIRQ_VERBOSE 0 +# define SOFTIRQ_VERBOSE 0 +#endif + +#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE +/* + * Quick filtering for interesting events: + */ +static int class_filter(struct lock_class *class) +{ +#if 0 + /* Example */ + if (class->name_version == 1 && + !strcmp(class->name, "lockname")) + return 1; + if (class->name_version == 1 && + !strcmp(class->name, "&struct->lockfield")) + return 1; +#endif + /* Filter everything else. 1 would be to allow everything else */ + return 0; +} +#endif + +static int verbose(struct lock_class *class) +{ +#if VERBOSE + return class_filter(class); +#endif + return 0; +} + +static void print_lockdep_off(const char *bug_msg) +{ + printk(KERN_DEBUG "%s\n", bug_msg); + printk(KERN_DEBUG "turning off the locking correctness validator.\n"); +#ifdef CONFIG_LOCK_STAT + printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n"); +#endif +} + +unsigned long nr_stack_trace_entries; + +#ifdef CONFIG_PROVE_LOCKING +/** + * struct lock_trace - single stack backtrace + * @hash_entry: Entry in a stack_trace_hash[] list. + * @hash: jhash() of @entries. + * @nr_entries: Number of entries in @entries. + * @entries: Actual stack backtrace. + */ +struct lock_trace { + struct hlist_node hash_entry; + u32 hash; + u32 nr_entries; + unsigned long entries[] __aligned(sizeof(unsigned long)); +}; +#define LOCK_TRACE_SIZE_IN_LONGS \ + (sizeof(struct lock_trace) / sizeof(unsigned long)) +/* + * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock. + */ +static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES]; +static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE]; + +static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2) +{ + return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries && + memcmp(t1->entries, t2->entries, + t1->nr_entries * sizeof(t1->entries[0])) == 0; +} + +static struct lock_trace *save_trace(void) +{ + struct lock_trace *trace, *t2; + struct hlist_head *hash_head; + u32 hash; + int max_entries; + + BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE); + BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES); + + trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries); + max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries - + LOCK_TRACE_SIZE_IN_LONGS; + + if (max_entries <= 0) { + if (!debug_locks_off_graph_unlock()) + return NULL; + + print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!"); + dump_stack(); + + return NULL; + } + trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3); + + hash = jhash(trace->entries, trace->nr_entries * + sizeof(trace->entries[0]), 0); + trace->hash = hash; + hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1)); + hlist_for_each_entry(t2, hash_head, hash_entry) { + if (traces_identical(trace, t2)) + return t2; + } + nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries; + hlist_add_head(&trace->hash_entry, hash_head); + + return trace; +} + +/* Return the number of stack traces in the stack_trace[] array. */ +u64 lockdep_stack_trace_count(void) +{ + struct lock_trace *trace; + u64 c = 0; + int i; + + for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) { + hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) { + c++; + } + } + + return c; +} + +/* Return the number of stack hash chains that have at least one stack trace. */ +u64 lockdep_stack_hash_count(void) +{ + u64 c = 0; + int i; + + for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) + if (!hlist_empty(&stack_trace_hash[i])) + c++; + + return c; +} +#endif + +unsigned int nr_hardirq_chains; +unsigned int nr_softirq_chains; +unsigned int nr_process_chains; +unsigned int max_lockdep_depth; + +#ifdef CONFIG_DEBUG_LOCKDEP +/* + * Various lockdep statistics: + */ +DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats); +#endif + +#ifdef CONFIG_PROVE_LOCKING +/* + * Locking printouts: + */ + +#define __USAGE(__STATE) \ + [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \ + [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \ + [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\ + [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R", + +static const char *usage_str[] = +{ +#define LOCKDEP_STATE(__STATE) __USAGE(__STATE) +#include "lockdep_states.h" +#undef LOCKDEP_STATE + [LOCK_USED] = "INITIAL USE", + [LOCK_USED_READ] = "INITIAL READ USE", + /* abused as string storage for verify_lock_unused() */ + [LOCK_USAGE_STATES] = "IN-NMI", +}; +#endif + +const char *__get_key_name(const struct lockdep_subclass_key *key, char *str) +{ + return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str); +} + +static inline unsigned long lock_flag(enum lock_usage_bit bit) +{ + return 1UL << bit; +} + +static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit) +{ + /* + * The usage character defaults to '.' (i.e., irqs disabled and not in + * irq context), which is the safest usage category. + */ + char c = '.'; + + /* + * The order of the following usage checks matters, which will + * result in the outcome character as follows: + * + * - '+': irq is enabled and not in irq context + * - '-': in irq context and irq is disabled + * - '?': in irq context and irq is enabled + */ + if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) { + c = '+'; + if (class->usage_mask & lock_flag(bit)) + c = '?'; + } else if (class->usage_mask & lock_flag(bit)) + c = '-'; + + return c; +} + +void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS]) +{ + int i = 0; + +#define LOCKDEP_STATE(__STATE) \ + usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \ + usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ); +#include "lockdep_states.h" +#undef LOCKDEP_STATE + + usage[i] = '\0'; +} + +static void __print_lock_name(struct lock_class *class) +{ + char str[KSYM_NAME_LEN]; + const char *name; + + name = class->name; + if (!name) { + name = __get_key_name(class->key, str); + printk(KERN_CONT "%s", name); + } else { + printk(KERN_CONT "%s", name); + if (class->name_version > 1) + printk(KERN_CONT "#%d", class->name_version); + if (class->subclass) + printk(KERN_CONT "/%d", class->subclass); + } +} + +static void print_lock_name(struct lock_class *class) +{ + char usage[LOCK_USAGE_CHARS]; + + get_usage_chars(class, usage); + + printk(KERN_CONT " ("); + __print_lock_name(class); + printk(KERN_CONT "){%s}-{%d:%d}", usage, + class->wait_type_outer ?: class->wait_type_inner, + class->wait_type_inner); +} + +static void print_lockdep_cache(struct lockdep_map *lock) +{ + const char *name; + char str[KSYM_NAME_LEN]; + + name = lock->name; + if (!name) + name = __get_key_name(lock->key->subkeys, str); + + printk(KERN_CONT "%s", name); +} + +static void print_lock(struct held_lock *hlock) +{ + /* + * We can be called locklessly through debug_show_all_locks() so be + * extra careful, the hlock might have been released and cleared. + * + * If this indeed happens, lets pretend it does not hurt to continue + * to print the lock unless the hlock class_idx does not point to a + * registered class. The rationale here is: since we don't attempt + * to distinguish whether we are in this situation, if it just + * happened we can't count on class_idx to tell either. + */ + struct lock_class *lock = hlock_class(hlock); + + if (!lock) { + printk(KERN_CONT "<RELEASED>\n"); + return; + } + + printk(KERN_CONT "%px", hlock->instance); + print_lock_name(lock); + printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip); +} + +static void lockdep_print_held_locks(struct task_struct *p) +{ + int i, depth = READ_ONCE(p->lockdep_depth); + + if (!depth) + printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p)); + else + printk("%d lock%s held by %s/%d:\n", depth, + depth > 1 ? "s" : "", p->comm, task_pid_nr(p)); + /* + * It's not reliable to print a task's held locks if it's not sleeping + * and it's not the current task. + */ + if (p != current && task_is_running(p)) + return; + for (i = 0; i < depth; i++) { + printk(" #%d: ", i); + print_lock(p->held_locks + i); + } +} + +static void print_kernel_ident(void) +{ + printk("%s %.*s %s\n", init_utsname()->release, + (int)strcspn(init_utsname()->version, " "), + init_utsname()->version, + print_tainted()); +} + +static int very_verbose(struct lock_class *class) +{ +#if VERY_VERBOSE + return class_filter(class); +#endif + return 0; +} + +/* + * Is this the address of a static object: + */ +#ifdef __KERNEL__ +static int static_obj(const void *obj) +{ + unsigned long addr = (unsigned long) obj; + + if (is_kernel_core_data(addr)) + return 1; + + /* + * keys are allowed in the __ro_after_init section. + */ + if (is_kernel_rodata(addr)) + return 1; + + /* + * in initdata section and used during bootup only? + * NOTE: On some platforms the initdata section is + * outside of the _stext ... _end range. + */ + if (system_state < SYSTEM_FREEING_INITMEM && + init_section_contains((void *)addr, 1)) + return 1; + + /* + * in-kernel percpu var? + */ + if (is_kernel_percpu_address(addr)) + return 1; + + /* + * module static or percpu var? + */ + return is_module_address(addr) || is_module_percpu_address(addr); +} +#endif + +/* + * To make lock name printouts unique, we calculate a unique + * class->name_version generation counter. The caller must hold the graph + * lock. + */ +static int count_matching_names(struct lock_class *new_class) +{ + struct lock_class *class; + int count = 0; + + if (!new_class->name) + return 0; + + list_for_each_entry(class, &all_lock_classes, lock_entry) { + if (new_class->key - new_class->subclass == class->key) + return class->name_version; + if (class->name && !strcmp(class->name, new_class->name)) + count = max(count, class->name_version); + } + + return count + 1; +} + +/* used from NMI context -- must be lockless */ +static noinstr struct lock_class * +look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass) +{ + struct lockdep_subclass_key *key; + struct hlist_head *hash_head; + struct lock_class *class; + + if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) { + instrumentation_begin(); + debug_locks_off(); + printk(KERN_ERR + "BUG: looking up invalid subclass: %u\n", subclass); + printk(KERN_ERR + "turning off the locking correctness validator.\n"); + dump_stack(); + instrumentation_end(); + return NULL; + } + + /* + * If it is not initialised then it has never been locked, + * so it won't be present in the hash table. + */ + if (unlikely(!lock->key)) + return NULL; + + /* + * NOTE: the class-key must be unique. For dynamic locks, a static + * lock_class_key variable is passed in through the mutex_init() + * (or spin_lock_init()) call - which acts as the key. For static + * locks we use the lock object itself as the key. + */ + BUILD_BUG_ON(sizeof(struct lock_class_key) > + sizeof(struct lockdep_map)); + + key = lock->key->subkeys + subclass; + + hash_head = classhashentry(key); + + /* + * We do an RCU walk of the hash, see lockdep_free_key_range(). + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return NULL; + + hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) { + if (class->key == key) { + /* + * Huh! same key, different name? Did someone trample + * on some memory? We're most confused. + */ + WARN_ONCE(class->name != lock->name && + lock->key != &__lockdep_no_validate__, + "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n", + lock->name, lock->key, class->name); + return class; + } + } + + return NULL; +} + +/* + * Static locks do not have their class-keys yet - for them the key is + * the lock object itself. If the lock is in the per cpu area, the + * canonical address of the lock (per cpu offset removed) is used. + */ +static bool assign_lock_key(struct lockdep_map *lock) +{ + unsigned long can_addr, addr = (unsigned long)lock; + +#ifdef __KERNEL__ + /* + * lockdep_free_key_range() assumes that struct lock_class_key + * objects do not overlap. Since we use the address of lock + * objects as class key for static objects, check whether the + * size of lock_class_key objects does not exceed the size of + * the smallest lock object. + */ + BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t)); +#endif + + if (__is_kernel_percpu_address(addr, &can_addr)) + lock->key = (void *)can_addr; + else if (__is_module_percpu_address(addr, &can_addr)) + lock->key = (void *)can_addr; + else if (static_obj(lock)) + lock->key = (void *)lock; + else { + /* Debug-check: all keys must be persistent! */ + debug_locks_off(); + pr_err("INFO: trying to register non-static key.\n"); + pr_err("The code is fine but needs lockdep annotation, or maybe\n"); + pr_err("you didn't initialize this object before use?\n"); + pr_err("turning off the locking correctness validator.\n"); + dump_stack(); + return false; + } + + return true; +} + +#ifdef CONFIG_DEBUG_LOCKDEP + +/* Check whether element @e occurs in list @h */ +static bool in_list(struct list_head *e, struct list_head *h) +{ + struct list_head *f; + + list_for_each(f, h) { + if (e == f) + return true; + } + + return false; +} + +/* + * Check whether entry @e occurs in any of the locks_after or locks_before + * lists. + */ +static bool in_any_class_list(struct list_head *e) +{ + struct lock_class *class; + int i; + + for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { + class = &lock_classes[i]; + if (in_list(e, &class->locks_after) || + in_list(e, &class->locks_before)) + return true; + } + return false; +} + +static bool class_lock_list_valid(struct lock_class *c, struct list_head *h) +{ + struct lock_list *e; + + list_for_each_entry(e, h, entry) { + if (e->links_to != c) { + printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s", + c->name ? : "(?)", + (unsigned long)(e - list_entries), + e->links_to && e->links_to->name ? + e->links_to->name : "(?)", + e->class && e->class->name ? e->class->name : + "(?)"); + return false; + } + } + return true; +} + +#ifdef CONFIG_PROVE_LOCKING +static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS]; +#endif + +static bool check_lock_chain_key(struct lock_chain *chain) +{ +#ifdef CONFIG_PROVE_LOCKING + u64 chain_key = INITIAL_CHAIN_KEY; + int i; + + for (i = chain->base; i < chain->base + chain->depth; i++) + chain_key = iterate_chain_key(chain_key, chain_hlocks[i]); + /* + * The 'unsigned long long' casts avoid that a compiler warning + * is reported when building tools/lib/lockdep. + */ + if (chain->chain_key != chain_key) { + printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n", + (unsigned long long)(chain - lock_chains), + (unsigned long long)chain->chain_key, + (unsigned long long)chain_key); + return false; + } +#endif + return true; +} + +static bool in_any_zapped_class_list(struct lock_class *class) +{ + struct pending_free *pf; + int i; + + for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) { + if (in_list(&class->lock_entry, &pf->zapped)) + return true; + } + + return false; +} + +static bool __check_data_structures(void) +{ + struct lock_class *class; + struct lock_chain *chain; + struct hlist_head *head; + struct lock_list *e; + int i; + + /* Check whether all classes occur in a lock list. */ + for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { + class = &lock_classes[i]; + if (!in_list(&class->lock_entry, &all_lock_classes) && + !in_list(&class->lock_entry, &free_lock_classes) && + !in_any_zapped_class_list(class)) { + printk(KERN_INFO "class %px/%s is not in any class list\n", + class, class->name ? : "(?)"); + return false; + } + } + + /* Check whether all classes have valid lock lists. */ + for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { + class = &lock_classes[i]; + if (!class_lock_list_valid(class, &class->locks_before)) + return false; + if (!class_lock_list_valid(class, &class->locks_after)) + return false; + } + + /* Check the chain_key of all lock chains. */ + for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) { + head = chainhash_table + i; + hlist_for_each_entry_rcu(chain, head, entry) { + if (!check_lock_chain_key(chain)) + return false; + } + } + + /* + * Check whether all list entries that are in use occur in a class + * lock list. + */ + for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { + e = list_entries + i; + if (!in_any_class_list(&e->entry)) { + printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n", + (unsigned int)(e - list_entries), + e->class->name ? : "(?)", + e->links_to->name ? : "(?)"); + return false; + } + } + + /* + * Check whether all list entries that are not in use do not occur in + * a class lock list. + */ + for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { + e = list_entries + i; + if (in_any_class_list(&e->entry)) { + printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n", + (unsigned int)(e - list_entries), + e->class && e->class->name ? e->class->name : + "(?)", + e->links_to && e->links_to->name ? + e->links_to->name : "(?)"); + return false; + } + } + + return true; +} + +int check_consistency = 0; +module_param(check_consistency, int, 0644); + +static void check_data_structures(void) +{ + static bool once = false; + + if (check_consistency && !once) { + if (!__check_data_structures()) { + once = true; + WARN_ON(once); + } + } +} + +#else /* CONFIG_DEBUG_LOCKDEP */ + +static inline void check_data_structures(void) { } + +#endif /* CONFIG_DEBUG_LOCKDEP */ + +static void init_chain_block_buckets(void); + +/* + * Initialize the lock_classes[] array elements, the free_lock_classes list + * and also the delayed_free structure. + */ +static void init_data_structures_once(void) +{ + static bool __read_mostly ds_initialized, rcu_head_initialized; + int i; + + if (likely(rcu_head_initialized)) + return; + + if (system_state >= SYSTEM_SCHEDULING) { + init_rcu_head(&delayed_free.rcu_head); + rcu_head_initialized = true; + } + + if (ds_initialized) + return; + + ds_initialized = true; + + INIT_LIST_HEAD(&delayed_free.pf[0].zapped); + INIT_LIST_HEAD(&delayed_free.pf[1].zapped); + + for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { + list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes); + INIT_LIST_HEAD(&lock_classes[i].locks_after); + INIT_LIST_HEAD(&lock_classes[i].locks_before); + } + init_chain_block_buckets(); +} + +static inline struct hlist_head *keyhashentry(const struct lock_class_key *key) +{ + unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS); + + return lock_keys_hash + hash; +} + +/* Register a dynamically allocated key. */ +void lockdep_register_key(struct lock_class_key *key) +{ + struct hlist_head *hash_head; + struct lock_class_key *k; + unsigned long flags; + + if (WARN_ON_ONCE(static_obj(key))) + return; + hash_head = keyhashentry(key); + + raw_local_irq_save(flags); + if (!graph_lock()) + goto restore_irqs; + hlist_for_each_entry_rcu(k, hash_head, hash_entry) { + if (WARN_ON_ONCE(k == key)) + goto out_unlock; + } + hlist_add_head_rcu(&key->hash_entry, hash_head); +out_unlock: + graph_unlock(); +restore_irqs: + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lockdep_register_key); + +/* Check whether a key has been registered as a dynamic key. */ +static bool is_dynamic_key(const struct lock_class_key *key) +{ + struct hlist_head *hash_head; + struct lock_class_key *k; + bool found = false; + + if (WARN_ON_ONCE(static_obj(key))) + return false; + + /* + * If lock debugging is disabled lock_keys_hash[] may contain + * pointers to memory that has already been freed. Avoid triggering + * a use-after-free in that case by returning early. + */ + if (!debug_locks) + return true; + + hash_head = keyhashentry(key); + + rcu_read_lock(); + hlist_for_each_entry_rcu(k, hash_head, hash_entry) { + if (k == key) { + found = true; + break; + } + } + rcu_read_unlock(); + + return found; +} + +/* + * Register a lock's class in the hash-table, if the class is not present + * yet. Otherwise we look it up. We cache the result in the lock object + * itself, so actual lookup of the hash should be once per lock object. + */ +static struct lock_class * +register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) +{ + struct lockdep_subclass_key *key; + struct hlist_head *hash_head; + struct lock_class *class; + int idx; + + DEBUG_LOCKS_WARN_ON(!irqs_disabled()); + + class = look_up_lock_class(lock, subclass); + if (likely(class)) + goto out_set_class_cache; + + if (!lock->key) { + if (!assign_lock_key(lock)) + return NULL; + } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) { + return NULL; + } + + key = lock->key->subkeys + subclass; + hash_head = classhashentry(key); + + if (!graph_lock()) { + return NULL; + } + /* + * We have to do the hash-walk again, to avoid races + * with another CPU: + */ + hlist_for_each_entry_rcu(class, hash_head, hash_entry) { + if (class->key == key) + goto out_unlock_set; + } + + init_data_structures_once(); + + /* Allocate a new lock class and add it to the hash. */ + class = list_first_entry_or_null(&free_lock_classes, typeof(*class), + lock_entry); + if (!class) { + if (!debug_locks_off_graph_unlock()) { + return NULL; + } + + print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!"); + dump_stack(); + return NULL; + } + nr_lock_classes++; + __set_bit(class - lock_classes, lock_classes_in_use); + debug_atomic_inc(nr_unused_locks); + class->key = key; + class->name = lock->name; + class->subclass = subclass; + WARN_ON_ONCE(!list_empty(&class->locks_before)); + WARN_ON_ONCE(!list_empty(&class->locks_after)); + class->name_version = count_matching_names(class); + class->wait_type_inner = lock->wait_type_inner; + class->wait_type_outer = lock->wait_type_outer; + class->lock_type = lock->lock_type; + /* + * We use RCU's safe list-add method to make + * parallel walking of the hash-list safe: + */ + hlist_add_head_rcu(&class->hash_entry, hash_head); + /* + * Remove the class from the free list and add it to the global list + * of classes. + */ + list_move_tail(&class->lock_entry, &all_lock_classes); + idx = class - lock_classes; + if (idx > max_lock_class_idx) + max_lock_class_idx = idx; + + if (verbose(class)) { + graph_unlock(); + + printk("\nnew class %px: %s", class->key, class->name); + if (class->name_version > 1) + printk(KERN_CONT "#%d", class->name_version); + printk(KERN_CONT "\n"); + dump_stack(); + + if (!graph_lock()) { + return NULL; + } + } +out_unlock_set: + graph_unlock(); + +out_set_class_cache: + if (!subclass || force) + lock->class_cache[0] = class; + else if (subclass < NR_LOCKDEP_CACHING_CLASSES) + lock->class_cache[subclass] = class; + + /* + * Hash collision, did we smoke some? We found a class with a matching + * hash but the subclass -- which is hashed in -- didn't match. + */ + if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass)) + return NULL; + + return class; +} + +#ifdef CONFIG_PROVE_LOCKING +/* + * Allocate a lockdep entry. (assumes the graph_lock held, returns + * with NULL on failure) + */ +static struct lock_list *alloc_list_entry(void) +{ + int idx = find_first_zero_bit(list_entries_in_use, + ARRAY_SIZE(list_entries)); + + if (idx >= ARRAY_SIZE(list_entries)) { + if (!debug_locks_off_graph_unlock()) + return NULL; + + print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!"); + dump_stack(); + return NULL; + } + nr_list_entries++; + __set_bit(idx, list_entries_in_use); + return list_entries + idx; +} + +/* + * Add a new dependency to the head of the list: + */ +static int add_lock_to_list(struct lock_class *this, + struct lock_class *links_to, struct list_head *head, + u16 distance, u8 dep, + const struct lock_trace *trace) +{ + struct lock_list *entry; + /* + * Lock not present yet - get a new dependency struct and + * add it to the list: + */ + entry = alloc_list_entry(); + if (!entry) + return 0; + + entry->class = this; + entry->links_to = links_to; + entry->dep = dep; + entry->distance = distance; + entry->trace = trace; + /* + * Both allocation and removal are done under the graph lock; but + * iteration is under RCU-sched; see look_up_lock_class() and + * lockdep_free_key_range(). + */ + list_add_tail_rcu(&entry->entry, head); + + return 1; +} + +/* + * For good efficiency of modular, we use power of 2 + */ +#define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS) +#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1) + +/* + * The circular_queue and helpers are used to implement graph + * breadth-first search (BFS) algorithm, by which we can determine + * whether there is a path from a lock to another. In deadlock checks, + * a path from the next lock to be acquired to a previous held lock + * indicates that adding the <prev> -> <next> lock dependency will + * produce a circle in the graph. Breadth-first search instead of + * depth-first search is used in order to find the shortest (circular) + * path. + */ +struct circular_queue { + struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE]; + unsigned int front, rear; +}; + +static struct circular_queue lock_cq; + +unsigned int max_bfs_queue_depth; + +static unsigned int lockdep_dependency_gen_id; + +static inline void __cq_init(struct circular_queue *cq) +{ + cq->front = cq->rear = 0; + lockdep_dependency_gen_id++; +} + +static inline int __cq_empty(struct circular_queue *cq) +{ + return (cq->front == cq->rear); +} + +static inline int __cq_full(struct circular_queue *cq) +{ + return ((cq->rear + 1) & CQ_MASK) == cq->front; +} + +static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem) +{ + if (__cq_full(cq)) + return -1; + + cq->element[cq->rear] = elem; + cq->rear = (cq->rear + 1) & CQ_MASK; + return 0; +} + +/* + * Dequeue an element from the circular_queue, return a lock_list if + * the queue is not empty, or NULL if otherwise. + */ +static inline struct lock_list * __cq_dequeue(struct circular_queue *cq) +{ + struct lock_list * lock; + + if (__cq_empty(cq)) + return NULL; + + lock = cq->element[cq->front]; + cq->front = (cq->front + 1) & CQ_MASK; + + return lock; +} + +static inline unsigned int __cq_get_elem_count(struct circular_queue *cq) +{ + return (cq->rear - cq->front) & CQ_MASK; +} + +static inline void mark_lock_accessed(struct lock_list *lock) +{ + lock->class->dep_gen_id = lockdep_dependency_gen_id; +} + +static inline void visit_lock_entry(struct lock_list *lock, + struct lock_list *parent) +{ + lock->parent = parent; +} + +static inline unsigned long lock_accessed(struct lock_list *lock) +{ + return lock->class->dep_gen_id == lockdep_dependency_gen_id; +} + +static inline struct lock_list *get_lock_parent(struct lock_list *child) +{ + return child->parent; +} + +static inline int get_lock_depth(struct lock_list *child) +{ + int depth = 0; + struct lock_list *parent; + + while ((parent = get_lock_parent(child))) { + child = parent; + depth++; + } + return depth; +} + +/* + * Return the forward or backward dependency list. + * + * @lock: the lock_list to get its class's dependency list + * @offset: the offset to struct lock_class to determine whether it is + * locks_after or locks_before + */ +static inline struct list_head *get_dep_list(struct lock_list *lock, int offset) +{ + void *lock_class = lock->class; + + return lock_class + offset; +} +/* + * Return values of a bfs search: + * + * BFS_E* indicates an error + * BFS_R* indicates a result (match or not) + * + * BFS_EINVALIDNODE: Find a invalid node in the graph. + * + * BFS_EQUEUEFULL: The queue is full while doing the bfs. + * + * BFS_RMATCH: Find the matched node in the graph, and put that node into + * *@target_entry. + * + * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry + * _unchanged_. + */ +enum bfs_result { + BFS_EINVALIDNODE = -2, + BFS_EQUEUEFULL = -1, + BFS_RMATCH = 0, + BFS_RNOMATCH = 1, +}; + +/* + * bfs_result < 0 means error + */ +static inline bool bfs_error(enum bfs_result res) +{ + return res < 0; +} + +/* + * DEP_*_BIT in lock_list::dep + * + * For dependency @prev -> @next: + * + * SR: @prev is shared reader (->read != 0) and @next is recursive reader + * (->read == 2) + * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader + * SN: @prev is shared reader and @next is non-recursive locker (->read != 2) + * EN: @prev is exclusive locker and @next is non-recursive locker + * + * Note that we define the value of DEP_*_BITs so that: + * bit0 is prev->read == 0 + * bit1 is next->read != 2 + */ +#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */ +#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */ +#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */ +#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */ + +#define DEP_SR_MASK (1U << (DEP_SR_BIT)) +#define DEP_ER_MASK (1U << (DEP_ER_BIT)) +#define DEP_SN_MASK (1U << (DEP_SN_BIT)) +#define DEP_EN_MASK (1U << (DEP_EN_BIT)) + +static inline unsigned int +__calc_dep_bit(struct held_lock *prev, struct held_lock *next) +{ + return (prev->read == 0) + ((next->read != 2) << 1); +} + +static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next) +{ + return 1U << __calc_dep_bit(prev, next); +} + +/* + * calculate the dep_bit for backwards edges. We care about whether @prev is + * shared and whether @next is recursive. + */ +static inline unsigned int +__calc_dep_bitb(struct held_lock *prev, struct held_lock *next) +{ + return (next->read != 2) + ((prev->read == 0) << 1); +} + +static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next) +{ + return 1U << __calc_dep_bitb(prev, next); +} + +/* + * Initialize a lock_list entry @lock belonging to @class as the root for a BFS + * search. + */ +static inline void __bfs_init_root(struct lock_list *lock, + struct lock_class *class) +{ + lock->class = class; + lock->parent = NULL; + lock->only_xr = 0; +} + +/* + * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the + * root for a BFS search. + * + * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure + * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)-> + * and -(S*)->. + */ +static inline void bfs_init_root(struct lock_list *lock, + struct held_lock *hlock) +{ + __bfs_init_root(lock, hlock_class(hlock)); + lock->only_xr = (hlock->read == 2); +} + +/* + * Similar to bfs_init_root() but initialize the root for backwards BFS. + * + * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure + * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not + * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->). + */ +static inline void bfs_init_rootb(struct lock_list *lock, + struct held_lock *hlock) +{ + __bfs_init_root(lock, hlock_class(hlock)); + lock->only_xr = (hlock->read != 0); +} + +static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset) +{ + if (!lock || !lock->parent) + return NULL; + + return list_next_or_null_rcu(get_dep_list(lock->parent, offset), + &lock->entry, struct lock_list, entry); +} + +/* + * Breadth-First Search to find a strong path in the dependency graph. + * + * @source_entry: the source of the path we are searching for. + * @data: data used for the second parameter of @match function + * @match: match function for the search + * @target_entry: pointer to the target of a matched path + * @offset: the offset to struct lock_class to determine whether it is + * locks_after or locks_before + * + * We may have multiple edges (considering different kinds of dependencies, + * e.g. ER and SN) between two nodes in the dependency graph. But + * only the strong dependency path in the graph is relevant to deadlocks. A + * strong dependency path is a dependency path that doesn't have two adjacent + * dependencies as -(*R)-> -(S*)->, please see: + * + * Documentation/locking/lockdep-design.rst + * + * for more explanation of the definition of strong dependency paths + * + * In __bfs(), we only traverse in the strong dependency path: + * + * In lock_list::only_xr, we record whether the previous dependency only + * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we + * filter out any -(S*)-> in the current dependency and after that, the + * ->only_xr is set according to whether we only have -(*R)-> left. + */ +static enum bfs_result __bfs(struct lock_list *source_entry, + void *data, + bool (*match)(struct lock_list *entry, void *data), + bool (*skip)(struct lock_list *entry, void *data), + struct lock_list **target_entry, + int offset) +{ + struct circular_queue *cq = &lock_cq; + struct lock_list *lock = NULL; + struct lock_list *entry; + struct list_head *head; + unsigned int cq_depth; + bool first; + + lockdep_assert_locked(); + + __cq_init(cq); + __cq_enqueue(cq, source_entry); + + while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) { + if (!lock->class) + return BFS_EINVALIDNODE; + + /* + * Step 1: check whether we already finish on this one. + * + * If we have visited all the dependencies from this @lock to + * others (iow, if we have visited all lock_list entries in + * @lock->class->locks_{after,before}) we skip, otherwise go + * and visit all the dependencies in the list and mark this + * list accessed. + */ + if (lock_accessed(lock)) + continue; + else + mark_lock_accessed(lock); + + /* + * Step 2: check whether prev dependency and this form a strong + * dependency path. + */ + if (lock->parent) { /* Parent exists, check prev dependency */ + u8 dep = lock->dep; + bool prev_only_xr = lock->parent->only_xr; + + /* + * Mask out all -(S*)-> if we only have *R in previous + * step, because -(*R)-> -(S*)-> don't make up a strong + * dependency. + */ + if (prev_only_xr) + dep &= ~(DEP_SR_MASK | DEP_SN_MASK); + + /* If nothing left, we skip */ + if (!dep) + continue; + + /* If there are only -(*R)-> left, set that for the next step */ + lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK)); + } + + /* + * Step 3: we haven't visited this and there is a strong + * dependency path to this, so check with @match. + * If @skip is provide and returns true, we skip this + * lock (and any path this lock is in). + */ + if (skip && skip(lock, data)) + continue; + + if (match(lock, data)) { + *target_entry = lock; + return BFS_RMATCH; + } + + /* + * Step 4: if not match, expand the path by adding the + * forward or backwards dependencies in the search + * + */ + first = true; + head = get_dep_list(lock, offset); + list_for_each_entry_rcu(entry, head, entry) { + visit_lock_entry(entry, lock); + + /* + * Note we only enqueue the first of the list into the + * queue, because we can always find a sibling + * dependency from one (see __bfs_next()), as a result + * the space of queue is saved. + */ + if (!first) + continue; + + first = false; + + if (__cq_enqueue(cq, entry)) + return BFS_EQUEUEFULL; + + cq_depth = __cq_get_elem_count(cq); + if (max_bfs_queue_depth < cq_depth) + max_bfs_queue_depth = cq_depth; + } + } + + return BFS_RNOMATCH; +} + +static inline enum bfs_result +__bfs_forwards(struct lock_list *src_entry, + void *data, + bool (*match)(struct lock_list *entry, void *data), + bool (*skip)(struct lock_list *entry, void *data), + struct lock_list **target_entry) +{ + return __bfs(src_entry, data, match, skip, target_entry, + offsetof(struct lock_class, locks_after)); + +} + +static inline enum bfs_result +__bfs_backwards(struct lock_list *src_entry, + void *data, + bool (*match)(struct lock_list *entry, void *data), + bool (*skip)(struct lock_list *entry, void *data), + struct lock_list **target_entry) +{ + return __bfs(src_entry, data, match, skip, target_entry, + offsetof(struct lock_class, locks_before)); + +} + +static void print_lock_trace(const struct lock_trace *trace, + unsigned int spaces) +{ + stack_trace_print(trace->entries, trace->nr_entries, spaces); +} + +/* + * Print a dependency chain entry (this is only done when a deadlock + * has been detected): + */ +static noinline void +print_circular_bug_entry(struct lock_list *target, int depth) +{ + if (debug_locks_silent) + return; + printk("\n-> #%u", depth); + print_lock_name(target->class); + printk(KERN_CONT ":\n"); + print_lock_trace(target->trace, 6); +} + +static void +print_circular_lock_scenario(struct held_lock *src, + struct held_lock *tgt, + struct lock_list *prt) +{ + struct lock_class *source = hlock_class(src); + struct lock_class *target = hlock_class(tgt); + struct lock_class *parent = prt->class; + + /* + * A direct locking problem where unsafe_class lock is taken + * directly by safe_class lock, then all we need to show + * is the deadlock scenario, as it is obvious that the + * unsafe lock is taken under the safe lock. + * + * But if there is a chain instead, where the safe lock takes + * an intermediate lock (middle_class) where this lock is + * not the same as the safe lock, then the lock chain is + * used to describe the problem. Otherwise we would need + * to show a different CPU case for each link in the chain + * from the safe_class lock to the unsafe_class lock. + */ + if (parent != source) { + printk("Chain exists of:\n "); + __print_lock_name(source); + printk(KERN_CONT " --> "); + __print_lock_name(parent); + printk(KERN_CONT " --> "); + __print_lock_name(target); + printk(KERN_CONT "\n\n"); + } + + printk(" Possible unsafe locking scenario:\n\n"); + printk(" CPU0 CPU1\n"); + printk(" ---- ----\n"); + printk(" lock("); + __print_lock_name(target); + printk(KERN_CONT ");\n"); + printk(" lock("); + __print_lock_name(parent); + printk(KERN_CONT ");\n"); + printk(" lock("); + __print_lock_name(target); + printk(KERN_CONT ");\n"); + printk(" lock("); + __print_lock_name(source); + printk(KERN_CONT ");\n"); + printk("\n *** DEADLOCK ***\n\n"); +} + +/* + * When a circular dependency is detected, print the + * header first: + */ +static noinline void +print_circular_bug_header(struct lock_list *entry, unsigned int depth, + struct held_lock *check_src, + struct held_lock *check_tgt) +{ + struct task_struct *curr = current; + + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("======================================================\n"); + pr_warn("WARNING: possible circular locking dependency detected\n"); + print_kernel_ident(); + pr_warn("------------------------------------------------------\n"); + pr_warn("%s/%d is trying to acquire lock:\n", + curr->comm, task_pid_nr(curr)); + print_lock(check_src); + + pr_warn("\nbut task is already holding lock:\n"); + + print_lock(check_tgt); + pr_warn("\nwhich lock already depends on the new lock.\n\n"); + pr_warn("\nthe existing dependency chain (in reverse order) is:\n"); + + print_circular_bug_entry(entry, depth); +} + +/* + * We are about to add A -> B into the dependency graph, and in __bfs() a + * strong dependency path A -> .. -> B is found: hlock_class equals + * entry->class. + * + * If A -> .. -> B can replace A -> B in any __bfs() search (means the former + * is _stronger_ than or equal to the latter), we consider A -> B as redundant. + * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A + * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the + * dependency graph, as any strong path ..-> A -> B ->.. we can get with + * having dependency A -> B, we could already get a equivalent path ..-> A -> + * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant. + * + * We need to make sure both the start and the end of A -> .. -> B is not + * weaker than A -> B. For the start part, please see the comment in + * check_redundant(). For the end part, we need: + * + * Either + * + * a) A -> B is -(*R)-> (everything is not weaker than that) + * + * or + * + * b) A -> .. -> B is -(*N)-> (nothing is stronger than this) + * + */ +static inline bool hlock_equal(struct lock_list *entry, void *data) +{ + struct held_lock *hlock = (struct held_lock *)data; + + return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */ + (hlock->read == 2 || /* A -> B is -(*R)-> */ + !entry->only_xr); /* A -> .. -> B is -(*N)-> */ +} + +/* + * We are about to add B -> A into the dependency graph, and in __bfs() a + * strong dependency path A -> .. -> B is found: hlock_class equals + * entry->class. + * + * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong + * dependency cycle, that means: + * + * Either + * + * a) B -> A is -(E*)-> + * + * or + * + * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B) + * + * as then we don't have -(*R)-> -(S*)-> in the cycle. + */ +static inline bool hlock_conflict(struct lock_list *entry, void *data) +{ + struct held_lock *hlock = (struct held_lock *)data; + + return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */ + (hlock->read == 0 || /* B -> A is -(E*)-> */ + !entry->only_xr); /* A -> .. -> B is -(*N)-> */ +} + +static noinline void print_circular_bug(struct lock_list *this, + struct lock_list *target, + struct held_lock *check_src, + struct held_lock *check_tgt) +{ + struct task_struct *curr = current; + struct lock_list *parent; + struct lock_list *first_parent; + int depth; + + if (!debug_locks_off_graph_unlock() || debug_locks_silent) + return; + + this->trace = save_trace(); + if (!this->trace) + return; + + depth = get_lock_depth(target); + + print_circular_bug_header(target, depth, check_src, check_tgt); + + parent = get_lock_parent(target); + first_parent = parent; + + while (parent) { + print_circular_bug_entry(parent, --depth); + parent = get_lock_parent(parent); + } + + printk("\nother info that might help us debug this:\n\n"); + print_circular_lock_scenario(check_src, check_tgt, + first_parent); + + lockdep_print_held_locks(curr); + + printk("\nstack backtrace:\n"); + dump_stack(); +} + +static noinline void print_bfs_bug(int ret) +{ + if (!debug_locks_off_graph_unlock()) + return; + + /* + * Breadth-first-search failed, graph got corrupted? + */ + WARN(1, "lockdep bfs error:%d\n", ret); +} + +static bool noop_count(struct lock_list *entry, void *data) +{ + (*(unsigned long *)data)++; + return false; +} + +static unsigned long __lockdep_count_forward_deps(struct lock_list *this) +{ + unsigned long count = 0; + struct lock_list *target_entry; + + __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry); + + return count; +} +unsigned long lockdep_count_forward_deps(struct lock_class *class) +{ + unsigned long ret, flags; + struct lock_list this; + + __bfs_init_root(&this, class); + + raw_local_irq_save(flags); + lockdep_lock(); + ret = __lockdep_count_forward_deps(&this); + lockdep_unlock(); + raw_local_irq_restore(flags); + + return ret; +} + +static unsigned long __lockdep_count_backward_deps(struct lock_list *this) +{ + unsigned long count = 0; + struct lock_list *target_entry; + + __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry); + + return count; +} + +unsigned long lockdep_count_backward_deps(struct lock_class *class) +{ + unsigned long ret, flags; + struct lock_list this; + + __bfs_init_root(&this, class); + + raw_local_irq_save(flags); + lockdep_lock(); + ret = __lockdep_count_backward_deps(&this); + lockdep_unlock(); + raw_local_irq_restore(flags); + + return ret; +} + +/* + * Check that the dependency graph starting at <src> can lead to + * <target> or not. + */ +static noinline enum bfs_result +check_path(struct held_lock *target, struct lock_list *src_entry, + bool (*match)(struct lock_list *entry, void *data), + bool (*skip)(struct lock_list *entry, void *data), + struct lock_list **target_entry) +{ + enum bfs_result ret; + + ret = __bfs_forwards(src_entry, target, match, skip, target_entry); + + if (unlikely(bfs_error(ret))) + print_bfs_bug(ret); + + return ret; +} + +/* + * Prove that the dependency graph starting at <src> can not + * lead to <target>. If it can, there is a circle when adding + * <target> -> <src> dependency. + * + * Print an error and return BFS_RMATCH if it does. + */ +static noinline enum bfs_result +check_noncircular(struct held_lock *src, struct held_lock *target, + struct lock_trace **const trace) +{ + enum bfs_result ret; + struct lock_list *target_entry; + struct lock_list src_entry; + + bfs_init_root(&src_entry, src); + + debug_atomic_inc(nr_cyclic_checks); + + ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry); + + if (unlikely(ret == BFS_RMATCH)) { + if (!*trace) { + /* + * If save_trace fails here, the printing might + * trigger a WARN but because of the !nr_entries it + * should not do bad things. + */ + *trace = save_trace(); + } + + print_circular_bug(&src_entry, target_entry, src, target); + } + + return ret; +} + +#ifdef CONFIG_TRACE_IRQFLAGS + +/* + * Forwards and backwards subgraph searching, for the purposes of + * proving that two subgraphs can be connected by a new dependency + * without creating any illegal irq-safe -> irq-unsafe lock dependency. + * + * A irq safe->unsafe deadlock happens with the following conditions: + * + * 1) We have a strong dependency path A -> ... -> B + * + * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore + * irq can create a new dependency B -> A (consider the case that a holder + * of B gets interrupted by an irq whose handler will try to acquire A). + * + * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a + * strong circle: + * + * For the usage bits of B: + * a) if A -> B is -(*N)->, then B -> A could be any type, so any + * ENABLED_IRQ usage suffices. + * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only + * ENABLED_IRQ_*_READ usage suffices. + * + * For the usage bits of A: + * c) if A -> B is -(E*)->, then B -> A could be any type, so any + * USED_IN_IRQ usage suffices. + * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only + * USED_IN_IRQ_*_READ usage suffices. + */ + +/* + * There is a strong dependency path in the dependency graph: A -> B, and now + * we need to decide which usage bit of A should be accumulated to detect + * safe->unsafe bugs. + * + * Note that usage_accumulate() is used in backwards search, so ->only_xr + * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true). + * + * As above, if only_xr is false, which means A -> B has -(E*)-> dependency + * path, any usage of A should be considered. Otherwise, we should only + * consider _READ usage. + */ +static inline bool usage_accumulate(struct lock_list *entry, void *mask) +{ + if (!entry->only_xr) + *(unsigned long *)mask |= entry->class->usage_mask; + else /* Mask out _READ usage bits */ + *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ); + + return false; +} + +/* + * There is a strong dependency path in the dependency graph: A -> B, and now + * we need to decide which usage bit of B conflicts with the usage bits of A, + * i.e. which usage bit of B may introduce safe->unsafe deadlocks. + * + * As above, if only_xr is false, which means A -> B has -(*N)-> dependency + * path, any usage of B should be considered. Otherwise, we should only + * consider _READ usage. + */ +static inline bool usage_match(struct lock_list *entry, void *mask) +{ + if (!entry->only_xr) + return !!(entry->class->usage_mask & *(unsigned long *)mask); + else /* Mask out _READ usage bits */ + return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask); +} + +static inline bool usage_skip(struct lock_list *entry, void *mask) +{ + /* + * Skip local_lock() for irq inversion detection. + * + * For !RT, local_lock() is not a real lock, so it won't carry any + * dependency. + * + * For RT, an irq inversion happens when we have lock A and B, and on + * some CPU we can have: + * + * lock(A); + * <interrupted> + * lock(B); + * + * where lock(B) cannot sleep, and we have a dependency B -> ... -> A. + * + * Now we prove local_lock() cannot exist in that dependency. First we + * have the observation for any lock chain L1 -> ... -> Ln, for any + * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise + * wait context check will complain. And since B is not a sleep lock, + * therefore B.inner_wait_type >= 2, and since the inner_wait_type of + * local_lock() is 3, which is greater than 2, therefore there is no + * way the local_lock() exists in the dependency B -> ... -> A. + * + * As a result, we will skip local_lock(), when we search for irq + * inversion bugs. + */ + if (entry->class->lock_type == LD_LOCK_PERCPU) { + if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG)) + return false; + + return true; + } + + return false; +} + +/* + * Find a node in the forwards-direction dependency sub-graph starting + * at @root->class that matches @bit. + * + * Return BFS_MATCH if such a node exists in the subgraph, and put that node + * into *@target_entry. + */ +static enum bfs_result +find_usage_forwards(struct lock_list *root, unsigned long usage_mask, + struct lock_list **target_entry) +{ + enum bfs_result result; + + debug_atomic_inc(nr_find_usage_forwards_checks); + + result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry); + + return result; +} + +/* + * Find a node in the backwards-direction dependency sub-graph starting + * at @root->class that matches @bit. + */ +static enum bfs_result +find_usage_backwards(struct lock_list *root, unsigned long usage_mask, + struct lock_list **target_entry) +{ + enum bfs_result result; + + debug_atomic_inc(nr_find_usage_backwards_checks); + + result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry); + + return result; +} + +static void print_lock_class_header(struct lock_class *class, int depth) +{ + int bit; + + printk("%*s->", depth, ""); + print_lock_name(class); +#ifdef CONFIG_DEBUG_LOCKDEP + printk(KERN_CONT " ops: %lu", debug_class_ops_read(class)); +#endif + printk(KERN_CONT " {\n"); + + for (bit = 0; bit < LOCK_TRACE_STATES; bit++) { + if (class->usage_mask & (1 << bit)) { + int len = depth; + + len += printk("%*s %s", depth, "", usage_str[bit]); + len += printk(KERN_CONT " at:\n"); + print_lock_trace(class->usage_traces[bit], len); + } + } + printk("%*s }\n", depth, ""); + + printk("%*s ... key at: [<%px>] %pS\n", + depth, "", class->key, class->key); +} + +/* + * Dependency path printing: + * + * After BFS we get a lock dependency path (linked via ->parent of lock_list), + * printing out each lock in the dependency path will help on understanding how + * the deadlock could happen. Here are some details about dependency path + * printing: + * + * 1) A lock_list can be either forwards or backwards for a lock dependency, + * for a lock dependency A -> B, there are two lock_lists: + * + * a) lock_list in the ->locks_after list of A, whose ->class is B and + * ->links_to is A. In this case, we can say the lock_list is + * "A -> B" (forwards case). + * + * b) lock_list in the ->locks_before list of B, whose ->class is A + * and ->links_to is B. In this case, we can say the lock_list is + * "B <- A" (bacwards case). + * + * The ->trace of both a) and b) point to the call trace where B was + * acquired with A held. + * + * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't + * represent a certain lock dependency, it only provides an initial entry + * for BFS. For example, BFS may introduce a "helper" lock_list whose + * ->class is A, as a result BFS will search all dependencies starting with + * A, e.g. A -> B or A -> C. + * + * The notation of a forwards helper lock_list is like "-> A", which means + * we should search the forwards dependencies starting with "A", e.g A -> B + * or A -> C. + * + * The notation of a bacwards helper lock_list is like "<- B", which means + * we should search the backwards dependencies ending with "B", e.g. + * B <- A or B <- C. + */ + +/* + * printk the shortest lock dependencies from @root to @leaf in reverse order. + * + * We have a lock dependency path as follow: + * + * @root @leaf + * | | + * V V + * ->parent ->parent + * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list | + * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln| + * + * , so it's natural that we start from @leaf and print every ->class and + * ->trace until we reach the @root. + */ +static void __used +print_shortest_lock_dependencies(struct lock_list *leaf, + struct lock_list *root) +{ + struct lock_list *entry = leaf; + int depth; + + /*compute depth from generated tree by BFS*/ + depth = get_lock_depth(leaf); + + do { + print_lock_class_header(entry->class, depth); + printk("%*s ... acquired at:\n", depth, ""); + print_lock_trace(entry->trace, 2); + printk("\n"); + + if (depth == 0 && (entry != root)) { + printk("lockdep:%s bad path found in chain graph\n", __func__); + break; + } + + entry = get_lock_parent(entry); + depth--; + } while (entry && (depth >= 0)); +} + +/* + * printk the shortest lock dependencies from @leaf to @root. + * + * We have a lock dependency path (from a backwards search) as follow: + * + * @leaf @root + * | | + * V V + * ->parent ->parent + * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list | + * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln | + * + * , so when we iterate from @leaf to @root, we actually print the lock + * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order. + * + * Another thing to notice here is that ->class of L2 <- L1 is L1, while the + * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call + * trace of L1 in the dependency path, which is alright, because most of the + * time we can figure out where L1 is held from the call trace of L2. + */ +static void __used +print_shortest_lock_dependencies_backwards(struct lock_list *leaf, + struct lock_list *root) +{ + struct lock_list *entry = leaf; + const struct lock_trace *trace = NULL; + int depth; + + /*compute depth from generated tree by BFS*/ + depth = get_lock_depth(leaf); + + do { + print_lock_class_header(entry->class, depth); + if (trace) { + printk("%*s ... acquired at:\n", depth, ""); + print_lock_trace(trace, 2); + printk("\n"); + } + + /* + * Record the pointer to the trace for the next lock_list + * entry, see the comments for the function. + */ + trace = entry->trace; + + if (depth == 0 && (entry != root)) { + printk("lockdep:%s bad path found in chain graph\n", __func__); + break; + } + + entry = get_lock_parent(entry); + depth--; + } while (entry && (depth >= 0)); +} + +static void +print_irq_lock_scenario(struct lock_list *safe_entry, + struct lock_list *unsafe_entry, + struct lock_class *prev_class, + struct lock_class *next_class) +{ + struct lock_class *safe_class = safe_entry->class; + struct lock_class *unsafe_class = unsafe_entry->class; + struct lock_class *middle_class = prev_class; + + if (middle_class == safe_class) + middle_class = next_class; + + /* + * A direct locking problem where unsafe_class lock is taken + * directly by safe_class lock, then all we need to show + * is the deadlock scenario, as it is obvious that the + * unsafe lock is taken under the safe lock. + * + * But if there is a chain instead, where the safe lock takes + * an intermediate lock (middle_class) where this lock is + * not the same as the safe lock, then the lock chain is + * used to describe the problem. Otherwise we would need + * to show a different CPU case for each link in the chain + * from the safe_class lock to the unsafe_class lock. + */ + if (middle_class != unsafe_class) { + printk("Chain exists of:\n "); + __print_lock_name(safe_class); + printk(KERN_CONT " --> "); + __print_lock_name(middle_class); + printk(KERN_CONT " --> "); + __print_lock_name(unsafe_class); + printk(KERN_CONT "\n\n"); + } + + printk(" Possible interrupt unsafe locking scenario:\n\n"); + printk(" CPU0 CPU1\n"); + printk(" ---- ----\n"); + printk(" lock("); + __print_lock_name(unsafe_class); + printk(KERN_CONT ");\n"); + printk(" local_irq_disable();\n"); + printk(" lock("); + __print_lock_name(safe_class); + printk(KERN_CONT ");\n"); + printk(" lock("); + __print_lock_name(middle_class); + printk(KERN_CONT ");\n"); + printk(" <Interrupt>\n"); + printk(" lock("); + __print_lock_name(safe_class); + printk(KERN_CONT ");\n"); + printk("\n *** DEADLOCK ***\n\n"); +} + +static void +print_bad_irq_dependency(struct task_struct *curr, + struct lock_list *prev_root, + struct lock_list *next_root, + struct lock_list *backwards_entry, + struct lock_list *forwards_entry, + struct held_lock *prev, + struct held_lock *next, + enum lock_usage_bit bit1, + enum lock_usage_bit bit2, + const char *irqclass) +{ + if (!debug_locks_off_graph_unlock() || debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("=====================================================\n"); + pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n", + irqclass, irqclass); + print_kernel_ident(); + pr_warn("-----------------------------------------------------\n"); + pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n", + curr->comm, task_pid_nr(curr), + lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT, + curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT, + lockdep_hardirqs_enabled(), + curr->softirqs_enabled); + print_lock(next); + + pr_warn("\nand this task is already holding:\n"); + print_lock(prev); + pr_warn("which would create a new lock dependency:\n"); + print_lock_name(hlock_class(prev)); + pr_cont(" ->"); + print_lock_name(hlock_class(next)); + pr_cont("\n"); + + pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n", + irqclass); + print_lock_name(backwards_entry->class); + pr_warn("\n... which became %s-irq-safe at:\n", irqclass); + + print_lock_trace(backwards_entry->class->usage_traces[bit1], 1); + + pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass); + print_lock_name(forwards_entry->class); + pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass); + pr_warn("..."); + + print_lock_trace(forwards_entry->class->usage_traces[bit2], 1); + + pr_warn("\nother info that might help us debug this:\n\n"); + print_irq_lock_scenario(backwards_entry, forwards_entry, + hlock_class(prev), hlock_class(next)); + + lockdep_print_held_locks(curr); + + pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass); + print_shortest_lock_dependencies_backwards(backwards_entry, prev_root); + + pr_warn("\nthe dependencies between the lock to be acquired"); + pr_warn(" and %s-irq-unsafe lock:\n", irqclass); + next_root->trace = save_trace(); + if (!next_root->trace) + return; + print_shortest_lock_dependencies(forwards_entry, next_root); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +static const char *state_names[] = { +#define LOCKDEP_STATE(__STATE) \ + __stringify(__STATE), +#include "lockdep_states.h" +#undef LOCKDEP_STATE +}; + +static const char *state_rnames[] = { +#define LOCKDEP_STATE(__STATE) \ + __stringify(__STATE)"-READ", +#include "lockdep_states.h" +#undef LOCKDEP_STATE +}; + +static inline const char *state_name(enum lock_usage_bit bit) +{ + if (bit & LOCK_USAGE_READ_MASK) + return state_rnames[bit >> LOCK_USAGE_DIR_MASK]; + else + return state_names[bit >> LOCK_USAGE_DIR_MASK]; +} + +/* + * The bit number is encoded like: + * + * bit0: 0 exclusive, 1 read lock + * bit1: 0 used in irq, 1 irq enabled + * bit2-n: state + */ +static int exclusive_bit(int new_bit) +{ + int state = new_bit & LOCK_USAGE_STATE_MASK; + int dir = new_bit & LOCK_USAGE_DIR_MASK; + + /* + * keep state, bit flip the direction and strip read. + */ + return state | (dir ^ LOCK_USAGE_DIR_MASK); +} + +/* + * Observe that when given a bitmask where each bitnr is encoded as above, a + * right shift of the mask transforms the individual bitnrs as -1 and + * conversely, a left shift transforms into +1 for the individual bitnrs. + * + * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can + * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0) + * instead by subtracting the bit number by 2, or shifting the mask right by 2. + * + * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2. + * + * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is + * all bits set) and recompose with bitnr1 flipped. + */ +static unsigned long invert_dir_mask(unsigned long mask) +{ + unsigned long excl = 0; + + /* Invert dir */ + excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK; + excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK; + + return excl; +} + +/* + * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ + * usage may cause deadlock too, for example: + * + * P1 P2 + * <irq disabled> + * write_lock(l1); <irq enabled> + * read_lock(l2); + * write_lock(l2); + * <in irq> + * read_lock(l1); + * + * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2 + * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible + * deadlock. + * + * In fact, all of the following cases may cause deadlocks: + * + * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_* + * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_* + * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ + * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ + * + * As a result, to calculate the "exclusive mask", first we invert the + * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with + * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all + * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*). + */ +static unsigned long exclusive_mask(unsigned long mask) +{ + unsigned long excl = invert_dir_mask(mask); + + excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK; + excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK; + + return excl; +} + +/* + * Retrieve the _possible_ original mask to which @mask is + * exclusive. Ie: this is the opposite of exclusive_mask(). + * Note that 2 possible original bits can match an exclusive + * bit: one has LOCK_USAGE_READ_MASK set, the other has it + * cleared. So both are returned for each exclusive bit. + */ +static unsigned long original_mask(unsigned long mask) +{ + unsigned long excl = invert_dir_mask(mask); + + /* Include read in existing usages */ + excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK; + excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK; + + return excl; +} + +/* + * Find the first pair of bit match between an original + * usage mask and an exclusive usage mask. + */ +static int find_exclusive_match(unsigned long mask, + unsigned long excl_mask, + enum lock_usage_bit *bitp, + enum lock_usage_bit *excl_bitp) +{ + int bit, excl, excl_read; + + for_each_set_bit(bit, &mask, LOCK_USED) { + /* + * exclusive_bit() strips the read bit, however, + * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need + * to search excl | LOCK_USAGE_READ_MASK as well. + */ + excl = exclusive_bit(bit); + excl_read = excl | LOCK_USAGE_READ_MASK; + if (excl_mask & lock_flag(excl)) { + *bitp = bit; + *excl_bitp = excl; + return 0; + } else if (excl_mask & lock_flag(excl_read)) { + *bitp = bit; + *excl_bitp = excl_read; + return 0; + } + } + return -1; +} + +/* + * Prove that the new dependency does not connect a hardirq-safe(-read) + * lock with a hardirq-unsafe lock - to achieve this we search + * the backwards-subgraph starting at <prev>, and the + * forwards-subgraph starting at <next>: + */ +static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, + struct held_lock *next) +{ + unsigned long usage_mask = 0, forward_mask, backward_mask; + enum lock_usage_bit forward_bit = 0, backward_bit = 0; + struct lock_list *target_entry1; + struct lock_list *target_entry; + struct lock_list this, that; + enum bfs_result ret; + + /* + * Step 1: gather all hard/soft IRQs usages backward in an + * accumulated usage mask. + */ + bfs_init_rootb(&this, prev); + + ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL); + if (bfs_error(ret)) { + print_bfs_bug(ret); + return 0; + } + + usage_mask &= LOCKF_USED_IN_IRQ_ALL; + if (!usage_mask) + return 1; + + /* + * Step 2: find exclusive uses forward that match the previous + * backward accumulated mask. + */ + forward_mask = exclusive_mask(usage_mask); + + bfs_init_root(&that, next); + + ret = find_usage_forwards(&that, forward_mask, &target_entry1); + if (bfs_error(ret)) { + print_bfs_bug(ret); + return 0; + } + if (ret == BFS_RNOMATCH) + return 1; + + /* + * Step 3: we found a bad match! Now retrieve a lock from the backward + * list whose usage mask matches the exclusive usage mask from the + * lock found on the forward list. + * + * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering + * the follow case: + * + * When trying to add A -> B to the graph, we find that there is a + * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M, + * that B -> ... -> M. However M is **softirq-safe**, if we use exact + * invert bits of M's usage_mask, we will find another lock N that is + * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not + * cause a inversion deadlock. + */ + backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL); + + ret = find_usage_backwards(&this, backward_mask, &target_entry); + if (bfs_error(ret)) { + print_bfs_bug(ret); + return 0; + } + if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH)) + return 1; + + /* + * Step 4: narrow down to a pair of incompatible usage bits + * and report it. + */ + ret = find_exclusive_match(target_entry->class->usage_mask, + target_entry1->class->usage_mask, + &backward_bit, &forward_bit); + if (DEBUG_LOCKS_WARN_ON(ret == -1)) + return 1; + + print_bad_irq_dependency(curr, &this, &that, + target_entry, target_entry1, + prev, next, + backward_bit, forward_bit, + state_name(backward_bit)); + + return 0; +} + +#else + +static inline int check_irq_usage(struct task_struct *curr, + struct held_lock *prev, struct held_lock *next) +{ + return 1; +} + +static inline bool usage_skip(struct lock_list *entry, void *mask) +{ + return false; +} + +#endif /* CONFIG_TRACE_IRQFLAGS */ + +#ifdef CONFIG_LOCKDEP_SMALL +/* + * Check that the dependency graph starting at <src> can lead to + * <target> or not. If it can, <src> -> <target> dependency is already + * in the graph. + * + * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if + * any error appears in the bfs search. + */ +static noinline enum bfs_result +check_redundant(struct held_lock *src, struct held_lock *target) +{ + enum bfs_result ret; + struct lock_list *target_entry; + struct lock_list src_entry; + + bfs_init_root(&src_entry, src); + /* + * Special setup for check_redundant(). + * + * To report redundant, we need to find a strong dependency path that + * is equal to or stronger than <src> -> <target>. So if <src> is E, + * we need to let __bfs() only search for a path starting at a -(E*)->, + * we achieve this by setting the initial node's ->only_xr to true in + * that case. And if <prev> is S, we set initial ->only_xr to false + * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant. + */ + src_entry.only_xr = src->read == 0; + + debug_atomic_inc(nr_redundant_checks); + + /* + * Note: we skip local_lock() for redundant check, because as the + * comment in usage_skip(), A -> local_lock() -> B and A -> B are not + * the same. + */ + ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry); + + if (ret == BFS_RMATCH) + debug_atomic_inc(nr_redundant); + + return ret; +} + +#else + +static inline enum bfs_result +check_redundant(struct held_lock *src, struct held_lock *target) +{ + return BFS_RNOMATCH; +} + +#endif + +static void inc_chains(int irq_context) +{ + if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT) + nr_hardirq_chains++; + else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT) + nr_softirq_chains++; + else + nr_process_chains++; +} + +static void dec_chains(int irq_context) +{ + if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT) + nr_hardirq_chains--; + else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT) + nr_softirq_chains--; + else + nr_process_chains--; +} + +static void +print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv) +{ + struct lock_class *next = hlock_class(nxt); + struct lock_class *prev = hlock_class(prv); + + printk(" Possible unsafe locking scenario:\n\n"); + printk(" CPU0\n"); + printk(" ----\n"); + printk(" lock("); + __print_lock_name(prev); + printk(KERN_CONT ");\n"); + printk(" lock("); + __print_lock_name(next); + printk(KERN_CONT ");\n"); + printk("\n *** DEADLOCK ***\n\n"); + printk(" May be due to missing lock nesting notation\n\n"); +} + +static void +print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, + struct held_lock *next) +{ + if (!debug_locks_off_graph_unlock() || debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("============================================\n"); + pr_warn("WARNING: possible recursive locking detected\n"); + print_kernel_ident(); + pr_warn("--------------------------------------------\n"); + pr_warn("%s/%d is trying to acquire lock:\n", + curr->comm, task_pid_nr(curr)); + print_lock(next); + pr_warn("\nbut task is already holding lock:\n"); + print_lock(prev); + + pr_warn("\nother info that might help us debug this:\n"); + print_deadlock_scenario(next, prev); + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +/* + * Check whether we are holding such a class already. + * + * (Note that this has to be done separately, because the graph cannot + * detect such classes of deadlocks.) + * + * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same + * lock class is held but nest_lock is also held, i.e. we rely on the + * nest_lock to avoid the deadlock. + */ +static int +check_deadlock(struct task_struct *curr, struct held_lock *next) +{ + struct held_lock *prev; + struct held_lock *nest = NULL; + int i; + + for (i = 0; i < curr->lockdep_depth; i++) { + prev = curr->held_locks + i; + + if (prev->instance == next->nest_lock) + nest = prev; + + if (hlock_class(prev) != hlock_class(next)) + continue; + + /* + * Allow read-after-read recursion of the same + * lock class (i.e. read_lock(lock)+read_lock(lock)): + */ + if ((next->read == 2) && prev->read) + continue; + + /* + * We're holding the nest_lock, which serializes this lock's + * nesting behaviour. + */ + if (nest) + return 2; + + print_deadlock_bug(curr, prev, next); + return 0; + } + return 1; +} + +/* + * There was a chain-cache miss, and we are about to add a new dependency + * to a previous lock. We validate the following rules: + * + * - would the adding of the <prev> -> <next> dependency create a + * circular dependency in the graph? [== circular deadlock] + * + * - does the new prev->next dependency connect any hardirq-safe lock + * (in the full backwards-subgraph starting at <prev>) with any + * hardirq-unsafe lock (in the full forwards-subgraph starting at + * <next>)? [== illegal lock inversion with hardirq contexts] + * + * - does the new prev->next dependency connect any softirq-safe lock + * (in the full backwards-subgraph starting at <prev>) with any + * softirq-unsafe lock (in the full forwards-subgraph starting at + * <next>)? [== illegal lock inversion with softirq contexts] + * + * any of these scenarios could lead to a deadlock. + * + * Then if all the validations pass, we add the forwards and backwards + * dependency. + */ +static int +check_prev_add(struct task_struct *curr, struct held_lock *prev, + struct held_lock *next, u16 distance, + struct lock_trace **const trace) +{ + struct lock_list *entry; + enum bfs_result ret; + + if (!hlock_class(prev)->key || !hlock_class(next)->key) { + /* + * The warning statements below may trigger a use-after-free + * of the class name. It is better to trigger a use-after free + * and to have the class name most of the time instead of not + * having the class name available. + */ + WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key, + "Detected use-after-free of lock class %px/%s\n", + hlock_class(prev), + hlock_class(prev)->name); + WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key, + "Detected use-after-free of lock class %px/%s\n", + hlock_class(next), + hlock_class(next)->name); + return 2; + } + + /* + * Prove that the new <prev> -> <next> dependency would not + * create a circular dependency in the graph. (We do this by + * a breadth-first search into the graph starting at <next>, + * and check whether we can reach <prev>.) + * + * The search is limited by the size of the circular queue (i.e., + * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes + * in the graph whose neighbours are to be checked. + */ + ret = check_noncircular(next, prev, trace); + if (unlikely(bfs_error(ret) || ret == BFS_RMATCH)) + return 0; + + if (!check_irq_usage(curr, prev, next)) + return 0; + + /* + * Is the <prev> -> <next> dependency already present? + * + * (this may occur even though this is a new chain: consider + * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3 + * chains - the second one will be new, but L1 already has + * L2 added to its dependency list, due to the first chain.) + */ + list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) { + if (entry->class == hlock_class(next)) { + if (distance == 1) + entry->distance = 1; + entry->dep |= calc_dep(prev, next); + + /* + * Also, update the reverse dependency in @next's + * ->locks_before list. + * + * Here we reuse @entry as the cursor, which is fine + * because we won't go to the next iteration of the + * outer loop: + * + * For normal cases, we return in the inner loop. + * + * If we fail to return, we have inconsistency, i.e. + * <prev>::locks_after contains <next> while + * <next>::locks_before doesn't contain <prev>. In + * that case, we return after the inner and indicate + * something is wrong. + */ + list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) { + if (entry->class == hlock_class(prev)) { + if (distance == 1) + entry->distance = 1; + entry->dep |= calc_depb(prev, next); + return 1; + } + } + + /* <prev> is not found in <next>::locks_before */ + return 0; + } + } + + /* + * Is the <prev> -> <next> link redundant? + */ + ret = check_redundant(prev, next); + if (bfs_error(ret)) + return 0; + else if (ret == BFS_RMATCH) + return 2; + + if (!*trace) { + *trace = save_trace(); + if (!*trace) + return 0; + } + + /* + * Ok, all validations passed, add the new lock + * to the previous lock's dependency list: + */ + ret = add_lock_to_list(hlock_class(next), hlock_class(prev), + &hlock_class(prev)->locks_after, distance, + calc_dep(prev, next), *trace); + + if (!ret) + return 0; + + ret = add_lock_to_list(hlock_class(prev), hlock_class(next), + &hlock_class(next)->locks_before, distance, + calc_depb(prev, next), *trace); + if (!ret) + return 0; + + return 2; +} + +/* + * Add the dependency to all directly-previous locks that are 'relevant'. + * The ones that are relevant are (in increasing distance from curr): + * all consecutive trylock entries and the final non-trylock entry - or + * the end of this context's lock-chain - whichever comes first. + */ +static int +check_prevs_add(struct task_struct *curr, struct held_lock *next) +{ + struct lock_trace *trace = NULL; + int depth = curr->lockdep_depth; + struct held_lock *hlock; + + /* + * Debugging checks. + * + * Depth must not be zero for a non-head lock: + */ + if (!depth) + goto out_bug; + /* + * At least two relevant locks must exist for this + * to be a head: + */ + if (curr->held_locks[depth].irq_context != + curr->held_locks[depth-1].irq_context) + goto out_bug; + + for (;;) { + u16 distance = curr->lockdep_depth - depth + 1; + hlock = curr->held_locks + depth - 1; + + if (hlock->check) { + int ret = check_prev_add(curr, hlock, next, distance, &trace); + if (!ret) + return 0; + + /* + * Stop after the first non-trylock entry, + * as non-trylock entries have added their + * own direct dependencies already, so this + * lock is connected to them indirectly: + */ + if (!hlock->trylock) + break; + } + + depth--; + /* + * End of lock-stack? + */ + if (!depth) + break; + /* + * Stop the search if we cross into another context: + */ + if (curr->held_locks[depth].irq_context != + curr->held_locks[depth-1].irq_context) + break; + } + return 1; +out_bug: + if (!debug_locks_off_graph_unlock()) + return 0; + + /* + * Clearly we all shouldn't be here, but since we made it we + * can reliable say we messed up our state. See the above two + * gotos for reasons why we could possibly end up here. + */ + WARN_ON(1); + + return 0; +} + +struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS]; +static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS); +static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS]; +unsigned long nr_zapped_lock_chains; +unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */ +unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */ +unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */ + +/* + * The first 2 chain_hlocks entries in the chain block in the bucket + * list contains the following meta data: + * + * entry[0]: + * Bit 15 - always set to 1 (it is not a class index) + * Bits 0-14 - upper 15 bits of the next block index + * entry[1] - lower 16 bits of next block index + * + * A next block index of all 1 bits means it is the end of the list. + * + * On the unsized bucket (bucket-0), the 3rd and 4th entries contain + * the chain block size: + * + * entry[2] - upper 16 bits of the chain block size + * entry[3] - lower 16 bits of the chain block size + */ +#define MAX_CHAIN_BUCKETS 16 +#define CHAIN_BLK_FLAG (1U << 15) +#define CHAIN_BLK_LIST_END 0xFFFFU + +static int chain_block_buckets[MAX_CHAIN_BUCKETS]; + +static inline int size_to_bucket(int size) +{ + if (size > MAX_CHAIN_BUCKETS) + return 0; + + return size - 1; +} + +/* + * Iterate all the chain blocks in a bucket. + */ +#define for_each_chain_block(bucket, prev, curr) \ + for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \ + (curr) >= 0; \ + (prev) = (curr), (curr) = chain_block_next(curr)) + +/* + * next block or -1 + */ +static inline int chain_block_next(int offset) +{ + int next = chain_hlocks[offset]; + + WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG)); + + if (next == CHAIN_BLK_LIST_END) + return -1; + + next &= ~CHAIN_BLK_FLAG; + next <<= 16; + next |= chain_hlocks[offset + 1]; + + return next; +} + +/* + * bucket-0 only + */ +static inline int chain_block_size(int offset) +{ + return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3]; +} + +static inline void init_chain_block(int offset, int next, int bucket, int size) +{ + chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG; + chain_hlocks[offset + 1] = (u16)next; + + if (size && !bucket) { + chain_hlocks[offset + 2] = size >> 16; + chain_hlocks[offset + 3] = (u16)size; + } +} + +static inline void add_chain_block(int offset, int size) +{ + int bucket = size_to_bucket(size); + int next = chain_block_buckets[bucket]; + int prev, curr; + + if (unlikely(size < 2)) { + /* + * We can't store single entries on the freelist. Leak them. + * + * One possible way out would be to uniquely mark them, other + * than with CHAIN_BLK_FLAG, such that we can recover them when + * the block before it is re-added. + */ + if (size) + nr_lost_chain_hlocks++; + return; + } + + nr_free_chain_hlocks += size; + if (!bucket) { + nr_large_chain_blocks++; + + /* + * Variable sized, sort large to small. + */ + for_each_chain_block(0, prev, curr) { + if (size >= chain_block_size(curr)) + break; + } + init_chain_block(offset, curr, 0, size); + if (prev < 0) + chain_block_buckets[0] = offset; + else + init_chain_block(prev, offset, 0, 0); + return; + } + /* + * Fixed size, add to head. + */ + init_chain_block(offset, next, bucket, size); + chain_block_buckets[bucket] = offset; +} + +/* + * Only the first block in the list can be deleted. + * + * For the variable size bucket[0], the first block (the largest one) is + * returned, broken up and put back into the pool. So if a chain block of + * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be + * queued up after the primordial chain block and never be used until the + * hlock entries in the primordial chain block is almost used up. That + * causes fragmentation and reduce allocation efficiency. That can be + * monitored by looking at the "large chain blocks" number in lockdep_stats. + */ +static inline void del_chain_block(int bucket, int size, int next) +{ + nr_free_chain_hlocks -= size; + chain_block_buckets[bucket] = next; + + if (!bucket) + nr_large_chain_blocks--; +} + +static void init_chain_block_buckets(void) +{ + int i; + + for (i = 0; i < MAX_CHAIN_BUCKETS; i++) + chain_block_buckets[i] = -1; + + add_chain_block(0, ARRAY_SIZE(chain_hlocks)); +} + +/* + * Return offset of a chain block of the right size or -1 if not found. + * + * Fairly simple worst-fit allocator with the addition of a number of size + * specific free lists. + */ +static int alloc_chain_hlocks(int req) +{ + int bucket, curr, size; + + /* + * We rely on the MSB to act as an escape bit to denote freelist + * pointers. Make sure this bit isn't set in 'normal' class_idx usage. + */ + BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG); + + init_data_structures_once(); + + if (nr_free_chain_hlocks < req) + return -1; + + /* + * We require a minimum of 2 (u16) entries to encode a freelist + * 'pointer'. + */ + req = max(req, 2); + bucket = size_to_bucket(req); + curr = chain_block_buckets[bucket]; + + if (bucket) { + if (curr >= 0) { + del_chain_block(bucket, req, chain_block_next(curr)); + return curr; + } + /* Try bucket 0 */ + curr = chain_block_buckets[0]; + } + + /* + * The variable sized freelist is sorted by size; the first entry is + * the largest. Use it if it fits. + */ + if (curr >= 0) { + size = chain_block_size(curr); + if (likely(size >= req)) { + del_chain_block(0, size, chain_block_next(curr)); + if (size > req) + add_chain_block(curr + req, size - req); + return curr; + } + } + + /* + * Last resort, split a block in a larger sized bucket. + */ + for (size = MAX_CHAIN_BUCKETS; size > req; size--) { + bucket = size_to_bucket(size); + curr = chain_block_buckets[bucket]; + if (curr < 0) + continue; + + del_chain_block(bucket, size, chain_block_next(curr)); + add_chain_block(curr + req, size - req); + return curr; + } + + return -1; +} + +static inline void free_chain_hlocks(int base, int size) +{ + add_chain_block(base, max(size, 2)); +} + +struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i) +{ + u16 chain_hlock = chain_hlocks[chain->base + i]; + unsigned int class_idx = chain_hlock_class_idx(chain_hlock); + + return lock_classes + class_idx; +} + +/* + * Returns the index of the first held_lock of the current chain + */ +static inline int get_first_held_lock(struct task_struct *curr, + struct held_lock *hlock) +{ + int i; + struct held_lock *hlock_curr; + + for (i = curr->lockdep_depth - 1; i >= 0; i--) { + hlock_curr = curr->held_locks + i; + if (hlock_curr->irq_context != hlock->irq_context) + break; + + } + + return ++i; +} + +#ifdef CONFIG_DEBUG_LOCKDEP +/* + * Returns the next chain_key iteration + */ +static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key) +{ + u64 new_chain_key = iterate_chain_key(chain_key, hlock_id); + + printk(" hlock_id:%d -> chain_key:%016Lx", + (unsigned int)hlock_id, + (unsigned long long)new_chain_key); + return new_chain_key; +} + +static void +print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next) +{ + struct held_lock *hlock; + u64 chain_key = INITIAL_CHAIN_KEY; + int depth = curr->lockdep_depth; + int i = get_first_held_lock(curr, hlock_next); + + printk("depth: %u (irq_context %u)\n", depth - i + 1, + hlock_next->irq_context); + for (; i < depth; i++) { + hlock = curr->held_locks + i; + chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key); + + print_lock(hlock); + } + + print_chain_key_iteration(hlock_id(hlock_next), chain_key); + print_lock(hlock_next); +} + +static void print_chain_keys_chain(struct lock_chain *chain) +{ + int i; + u64 chain_key = INITIAL_CHAIN_KEY; + u16 hlock_id; + + printk("depth: %u\n", chain->depth); + for (i = 0; i < chain->depth; i++) { + hlock_id = chain_hlocks[chain->base + i]; + chain_key = print_chain_key_iteration(hlock_id, chain_key); + + print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id)); + printk("\n"); + } +} + +static void print_collision(struct task_struct *curr, + struct held_lock *hlock_next, + struct lock_chain *chain) +{ + pr_warn("\n"); + pr_warn("============================\n"); + pr_warn("WARNING: chain_key collision\n"); + print_kernel_ident(); + pr_warn("----------------------------\n"); + pr_warn("%s/%d: ", current->comm, task_pid_nr(current)); + pr_warn("Hash chain already cached but the contents don't match!\n"); + + pr_warn("Held locks:"); + print_chain_keys_held_locks(curr, hlock_next); + + pr_warn("Locks in cached chain:"); + print_chain_keys_chain(chain); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} +#endif + +/* + * Checks whether the chain and the current held locks are consistent + * in depth and also in content. If they are not it most likely means + * that there was a collision during the calculation of the chain_key. + * Returns: 0 not passed, 1 passed + */ +static int check_no_collision(struct task_struct *curr, + struct held_lock *hlock, + struct lock_chain *chain) +{ +#ifdef CONFIG_DEBUG_LOCKDEP + int i, j, id; + + i = get_first_held_lock(curr, hlock); + + if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) { + print_collision(curr, hlock, chain); + return 0; + } + + for (j = 0; j < chain->depth - 1; j++, i++) { + id = hlock_id(&curr->held_locks[i]); + + if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) { + print_collision(curr, hlock, chain); + return 0; + } + } +#endif + return 1; +} + +/* + * Given an index that is >= -1, return the index of the next lock chain. + * Return -2 if there is no next lock chain. + */ +long lockdep_next_lockchain(long i) +{ + i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1); + return i < ARRAY_SIZE(lock_chains) ? i : -2; +} + +unsigned long lock_chain_count(void) +{ + return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains)); +} + +/* Must be called with the graph lock held. */ +static struct lock_chain *alloc_lock_chain(void) +{ + int idx = find_first_zero_bit(lock_chains_in_use, + ARRAY_SIZE(lock_chains)); + + if (unlikely(idx >= ARRAY_SIZE(lock_chains))) + return NULL; + __set_bit(idx, lock_chains_in_use); + return lock_chains + idx; +} + +/* + * Adds a dependency chain into chain hashtable. And must be called with + * graph_lock held. + * + * Return 0 if fail, and graph_lock is released. + * Return 1 if succeed, with graph_lock held. + */ +static inline int add_chain_cache(struct task_struct *curr, + struct held_lock *hlock, + u64 chain_key) +{ + struct hlist_head *hash_head = chainhashentry(chain_key); + struct lock_chain *chain; + int i, j; + + /* + * The caller must hold the graph lock, ensure we've got IRQs + * disabled to make this an IRQ-safe lock.. for recursion reasons + * lockdep won't complain about its own locking errors. + */ + if (lockdep_assert_locked()) + return 0; + + chain = alloc_lock_chain(); + if (!chain) { + if (!debug_locks_off_graph_unlock()) + return 0; + + print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!"); + dump_stack(); + return 0; + } + chain->chain_key = chain_key; + chain->irq_context = hlock->irq_context; + i = get_first_held_lock(curr, hlock); + chain->depth = curr->lockdep_depth + 1 - i; + + BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks)); + BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks)); + BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes)); + + j = alloc_chain_hlocks(chain->depth); + if (j < 0) { + if (!debug_locks_off_graph_unlock()) + return 0; + + print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!"); + dump_stack(); + return 0; + } + + chain->base = j; + for (j = 0; j < chain->depth - 1; j++, i++) { + int lock_id = hlock_id(curr->held_locks + i); + + chain_hlocks[chain->base + j] = lock_id; + } + chain_hlocks[chain->base + j] = hlock_id(hlock); + hlist_add_head_rcu(&chain->entry, hash_head); + debug_atomic_inc(chain_lookup_misses); + inc_chains(chain->irq_context); + + return 1; +} + +/* + * Look up a dependency chain. Must be called with either the graph lock or + * the RCU read lock held. + */ +static inline struct lock_chain *lookup_chain_cache(u64 chain_key) +{ + struct hlist_head *hash_head = chainhashentry(chain_key); + struct lock_chain *chain; + + hlist_for_each_entry_rcu(chain, hash_head, entry) { + if (READ_ONCE(chain->chain_key) == chain_key) { + debug_atomic_inc(chain_lookup_hits); + return chain; + } + } + return NULL; +} + +/* + * If the key is not present yet in dependency chain cache then + * add it and return 1 - in this case the new dependency chain is + * validated. If the key is already hashed, return 0. + * (On return with 1 graph_lock is held.) + */ +static inline int lookup_chain_cache_add(struct task_struct *curr, + struct held_lock *hlock, + u64 chain_key) +{ + struct lock_class *class = hlock_class(hlock); + struct lock_chain *chain = lookup_chain_cache(chain_key); + + if (chain) { +cache_hit: + if (!check_no_collision(curr, hlock, chain)) + return 0; + + if (very_verbose(class)) { + printk("\nhash chain already cached, key: " + "%016Lx tail class: [%px] %s\n", + (unsigned long long)chain_key, + class->key, class->name); + } + + return 0; + } + + if (very_verbose(class)) { + printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n", + (unsigned long long)chain_key, class->key, class->name); + } + + if (!graph_lock()) + return 0; + + /* + * We have to walk the chain again locked - to avoid duplicates: + */ + chain = lookup_chain_cache(chain_key); + if (chain) { + graph_unlock(); + goto cache_hit; + } + + if (!add_chain_cache(curr, hlock, chain_key)) + return 0; + + return 1; +} + +static int validate_chain(struct task_struct *curr, + struct held_lock *hlock, + int chain_head, u64 chain_key) +{ + /* + * Trylock needs to maintain the stack of held locks, but it + * does not add new dependencies, because trylock can be done + * in any order. + * + * We look up the chain_key and do the O(N^2) check and update of + * the dependencies only if this is a new dependency chain. + * (If lookup_chain_cache_add() return with 1 it acquires + * graph_lock for us) + */ + if (!hlock->trylock && hlock->check && + lookup_chain_cache_add(curr, hlock, chain_key)) { + /* + * Check whether last held lock: + * + * - is irq-safe, if this lock is irq-unsafe + * - is softirq-safe, if this lock is hardirq-unsafe + * + * And check whether the new lock's dependency graph + * could lead back to the previous lock: + * + * - within the current held-lock stack + * - across our accumulated lock dependency records + * + * any of these scenarios could lead to a deadlock. + */ + /* + * The simple case: does the current hold the same lock + * already? + */ + int ret = check_deadlock(curr, hlock); + + if (!ret) + return 0; + /* + * Add dependency only if this lock is not the head + * of the chain, and if the new lock introduces no more + * lock dependency (because we already hold a lock with the + * same lock class) nor deadlock (because the nest_lock + * serializes nesting locks), see the comments for + * check_deadlock(). + */ + if (!chain_head && ret != 2) { + if (!check_prevs_add(curr, hlock)) + return 0; + } + + graph_unlock(); + } else { + /* after lookup_chain_cache_add(): */ + if (unlikely(!debug_locks)) + return 0; + } + + return 1; +} +#else +static inline int validate_chain(struct task_struct *curr, + struct held_lock *hlock, + int chain_head, u64 chain_key) +{ + return 1; +} + +static void init_chain_block_buckets(void) { } +#endif /* CONFIG_PROVE_LOCKING */ + +/* + * We are building curr_chain_key incrementally, so double-check + * it from scratch, to make sure that it's done correctly: + */ +static void check_chain_key(struct task_struct *curr) +{ +#ifdef CONFIG_DEBUG_LOCKDEP + struct held_lock *hlock, *prev_hlock = NULL; + unsigned int i; + u64 chain_key = INITIAL_CHAIN_KEY; + + for (i = 0; i < curr->lockdep_depth; i++) { + hlock = curr->held_locks + i; + if (chain_key != hlock->prev_chain_key) { + debug_locks_off(); + /* + * We got mighty confused, our chain keys don't match + * with what we expect, someone trample on our task state? + */ + WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n", + curr->lockdep_depth, i, + (unsigned long long)chain_key, + (unsigned long long)hlock->prev_chain_key); + return; + } + + /* + * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is + * it registered lock class index? + */ + if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use))) + return; + + if (prev_hlock && (prev_hlock->irq_context != + hlock->irq_context)) + chain_key = INITIAL_CHAIN_KEY; + chain_key = iterate_chain_key(chain_key, hlock_id(hlock)); + prev_hlock = hlock; + } + if (chain_key != curr->curr_chain_key) { + debug_locks_off(); + /* + * More smoking hash instead of calculating it, damn see these + * numbers float.. I bet that a pink elephant stepped on my memory. + */ + WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n", + curr->lockdep_depth, i, + (unsigned long long)chain_key, + (unsigned long long)curr->curr_chain_key); + } +#endif +} + +#ifdef CONFIG_PROVE_LOCKING +static int mark_lock(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit new_bit); + +static void print_usage_bug_scenario(struct held_lock *lock) +{ + struct lock_class *class = hlock_class(lock); + + printk(" Possible unsafe locking scenario:\n\n"); + printk(" CPU0\n"); + printk(" ----\n"); + printk(" lock("); + __print_lock_name(class); + printk(KERN_CONT ");\n"); + printk(" <Interrupt>\n"); + printk(" lock("); + __print_lock_name(class); + printk(KERN_CONT ");\n"); + printk("\n *** DEADLOCK ***\n\n"); +} + +static void +print_usage_bug(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit) +{ + if (!debug_locks_off() || debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("================================\n"); + pr_warn("WARNING: inconsistent lock state\n"); + print_kernel_ident(); + pr_warn("--------------------------------\n"); + + pr_warn("inconsistent {%s} -> {%s} usage.\n", + usage_str[prev_bit], usage_str[new_bit]); + + pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n", + curr->comm, task_pid_nr(curr), + lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT, + lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT, + lockdep_hardirqs_enabled(), + lockdep_softirqs_enabled(curr)); + print_lock(this); + + pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]); + print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1); + + print_irqtrace_events(curr); + pr_warn("\nother info that might help us debug this:\n"); + print_usage_bug_scenario(this); + + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +/* + * Print out an error if an invalid bit is set: + */ +static inline int +valid_state(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit) +{ + if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) { + graph_unlock(); + print_usage_bug(curr, this, bad_bit, new_bit); + return 0; + } + return 1; +} + + +/* + * print irq inversion bug: + */ +static void +print_irq_inversion_bug(struct task_struct *curr, + struct lock_list *root, struct lock_list *other, + struct held_lock *this, int forwards, + const char *irqclass) +{ + struct lock_list *entry = other; + struct lock_list *middle = NULL; + int depth; + + if (!debug_locks_off_graph_unlock() || debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("========================================================\n"); + pr_warn("WARNING: possible irq lock inversion dependency detected\n"); + print_kernel_ident(); + pr_warn("--------------------------------------------------------\n"); + pr_warn("%s/%d just changed the state of lock:\n", + curr->comm, task_pid_nr(curr)); + print_lock(this); + if (forwards) + pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass); + else + pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass); + print_lock_name(other->class); + pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n"); + + pr_warn("\nother info that might help us debug this:\n"); + + /* Find a middle lock (if one exists) */ + depth = get_lock_depth(other); + do { + if (depth == 0 && (entry != root)) { + pr_warn("lockdep:%s bad path found in chain graph\n", __func__); + break; + } + middle = entry; + entry = get_lock_parent(entry); + depth--; + } while (entry && entry != root && (depth >= 0)); + if (forwards) + print_irq_lock_scenario(root, other, + middle ? middle->class : root->class, other->class); + else + print_irq_lock_scenario(other, root, + middle ? middle->class : other->class, root->class); + + lockdep_print_held_locks(curr); + + pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n"); + root->trace = save_trace(); + if (!root->trace) + return; + print_shortest_lock_dependencies(other, root); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +/* + * Prove that in the forwards-direction subgraph starting at <this> + * there is no lock matching <mask>: + */ +static int +check_usage_forwards(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit bit) +{ + enum bfs_result ret; + struct lock_list root; + struct lock_list *target_entry; + enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK; + unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit); + + bfs_init_root(&root, this); + ret = find_usage_forwards(&root, usage_mask, &target_entry); + if (bfs_error(ret)) { + print_bfs_bug(ret); + return 0; + } + if (ret == BFS_RNOMATCH) + return 1; + + /* Check whether write or read usage is the match */ + if (target_entry->class->usage_mask & lock_flag(bit)) { + print_irq_inversion_bug(curr, &root, target_entry, + this, 1, state_name(bit)); + } else { + print_irq_inversion_bug(curr, &root, target_entry, + this, 1, state_name(read_bit)); + } + + return 0; +} + +/* + * Prove that in the backwards-direction subgraph starting at <this> + * there is no lock matching <mask>: + */ +static int +check_usage_backwards(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit bit) +{ + enum bfs_result ret; + struct lock_list root; + struct lock_list *target_entry; + enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK; + unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit); + + bfs_init_rootb(&root, this); + ret = find_usage_backwards(&root, usage_mask, &target_entry); + if (bfs_error(ret)) { + print_bfs_bug(ret); + return 0; + } + if (ret == BFS_RNOMATCH) + return 1; + + /* Check whether write or read usage is the match */ + if (target_entry->class->usage_mask & lock_flag(bit)) { + print_irq_inversion_bug(curr, &root, target_entry, + this, 0, state_name(bit)); + } else { + print_irq_inversion_bug(curr, &root, target_entry, + this, 0, state_name(read_bit)); + } + + return 0; +} + +void print_irqtrace_events(struct task_struct *curr) +{ + const struct irqtrace_events *trace = &curr->irqtrace; + + printk("irq event stamp: %u\n", trace->irq_events); + printk("hardirqs last enabled at (%u): [<%px>] %pS\n", + trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip, + (void *)trace->hardirq_enable_ip); + printk("hardirqs last disabled at (%u): [<%px>] %pS\n", + trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip, + (void *)trace->hardirq_disable_ip); + printk("softirqs last enabled at (%u): [<%px>] %pS\n", + trace->softirq_enable_event, (void *)trace->softirq_enable_ip, + (void *)trace->softirq_enable_ip); + printk("softirqs last disabled at (%u): [<%px>] %pS\n", + trace->softirq_disable_event, (void *)trace->softirq_disable_ip, + (void *)trace->softirq_disable_ip); +} + +static int HARDIRQ_verbose(struct lock_class *class) +{ +#if HARDIRQ_VERBOSE + return class_filter(class); +#endif + return 0; +} + +static int SOFTIRQ_verbose(struct lock_class *class) +{ +#if SOFTIRQ_VERBOSE + return class_filter(class); +#endif + return 0; +} + +static int (*state_verbose_f[])(struct lock_class *class) = { +#define LOCKDEP_STATE(__STATE) \ + __STATE##_verbose, +#include "lockdep_states.h" +#undef LOCKDEP_STATE +}; + +static inline int state_verbose(enum lock_usage_bit bit, + struct lock_class *class) +{ + return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class); +} + +typedef int (*check_usage_f)(struct task_struct *, struct held_lock *, + enum lock_usage_bit bit, const char *name); + +static int +mark_lock_irq(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit new_bit) +{ + int excl_bit = exclusive_bit(new_bit); + int read = new_bit & LOCK_USAGE_READ_MASK; + int dir = new_bit & LOCK_USAGE_DIR_MASK; + + /* + * Validate that this particular lock does not have conflicting + * usage states. + */ + if (!valid_state(curr, this, new_bit, excl_bit)) + return 0; + + /* + * Check for read in write conflicts + */ + if (!read && !valid_state(curr, this, new_bit, + excl_bit + LOCK_USAGE_READ_MASK)) + return 0; + + + /* + * Validate that the lock dependencies don't have conflicting usage + * states. + */ + if (dir) { + /* + * mark ENABLED has to look backwards -- to ensure no dependee + * has USED_IN state, which, again, would allow recursion deadlocks. + */ + if (!check_usage_backwards(curr, this, excl_bit)) + return 0; + } else { + /* + * mark USED_IN has to look forwards -- to ensure no dependency + * has ENABLED state, which would allow recursion deadlocks. + */ + if (!check_usage_forwards(curr, this, excl_bit)) + return 0; + } + + if (state_verbose(new_bit, hlock_class(this))) + return 2; + + return 1; +} + +/* + * Mark all held locks with a usage bit: + */ +static int +mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit) +{ + struct held_lock *hlock; + int i; + + for (i = 0; i < curr->lockdep_depth; i++) { + enum lock_usage_bit hlock_bit = base_bit; + hlock = curr->held_locks + i; + + if (hlock->read) + hlock_bit += LOCK_USAGE_READ_MASK; + + BUG_ON(hlock_bit >= LOCK_USAGE_STATES); + + if (!hlock->check) + continue; + + if (!mark_lock(curr, hlock, hlock_bit)) + return 0; + } + + return 1; +} + +/* + * Hardirqs will be enabled: + */ +static void __trace_hardirqs_on_caller(void) +{ + struct task_struct *curr = current; + + /* + * We are going to turn hardirqs on, so set the + * usage bit for all held locks: + */ + if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ)) + return; + /* + * If we have softirqs enabled, then set the usage + * bit for all held locks. (disabled hardirqs prevented + * this bit from being set before) + */ + if (curr->softirqs_enabled) + mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ); +} + +/** + * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts + * + * Invoked before a possible transition to RCU idle from exit to user or + * guest mode. This ensures that all RCU operations are done before RCU + * stops watching. After the RCU transition lockdep_hardirqs_on() has to be + * invoked to set the final state. + */ +void lockdep_hardirqs_on_prepare(void) +{ + if (unlikely(!debug_locks)) + return; + + /* + * NMIs do not (and cannot) track lock dependencies, nothing to do. + */ + if (unlikely(in_nmi())) + return; + + if (unlikely(this_cpu_read(lockdep_recursion))) + return; + + if (unlikely(lockdep_hardirqs_enabled())) { + /* + * Neither irq nor preemption are disabled here + * so this is racy by nature but losing one hit + * in a stat is not a big deal. + */ + __debug_atomic_inc(redundant_hardirqs_on); + return; + } + + /* + * We're enabling irqs and according to our state above irqs weren't + * already enabled, yet we find the hardware thinks they are in fact + * enabled.. someone messed up their IRQ state tracing. + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return; + + /* + * See the fine text that goes along with this variable definition. + */ + if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled)) + return; + + /* + * Can't allow enabling interrupts while in an interrupt handler, + * that's general bad form and such. Recursion, limited stack etc.. + */ + if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context())) + return; + + current->hardirq_chain_key = current->curr_chain_key; + + lockdep_recursion_inc(); + __trace_hardirqs_on_caller(); + lockdep_recursion_finish(); +} +EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare); + +void noinstr lockdep_hardirqs_on(unsigned long ip) +{ + struct irqtrace_events *trace = ¤t->irqtrace; + + if (unlikely(!debug_locks)) + return; + + /* + * NMIs can happen in the middle of local_irq_{en,dis}able() where the + * tracking state and hardware state are out of sync. + * + * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from, + * and not rely on hardware state like normal interrupts. + */ + if (unlikely(in_nmi())) { + if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) + return; + + /* + * Skip: + * - recursion check, because NMI can hit lockdep; + * - hardware state check, because above; + * - chain_key check, see lockdep_hardirqs_on_prepare(). + */ + goto skip_checks; + } + + if (unlikely(this_cpu_read(lockdep_recursion))) + return; + + if (lockdep_hardirqs_enabled()) { + /* + * Neither irq nor preemption are disabled here + * so this is racy by nature but losing one hit + * in a stat is not a big deal. + */ + __debug_atomic_inc(redundant_hardirqs_on); + return; + } + + /* + * We're enabling irqs and according to our state above irqs weren't + * already enabled, yet we find the hardware thinks they are in fact + * enabled.. someone messed up their IRQ state tracing. + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return; + + /* + * Ensure the lock stack remained unchanged between + * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on(). + */ + DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key != + current->curr_chain_key); + +skip_checks: + /* we'll do an OFF -> ON transition: */ + __this_cpu_write(hardirqs_enabled, 1); + trace->hardirq_enable_ip = ip; + trace->hardirq_enable_event = ++trace->irq_events; + debug_atomic_inc(hardirqs_on_events); +} +EXPORT_SYMBOL_GPL(lockdep_hardirqs_on); + +/* + * Hardirqs were disabled: + */ +void noinstr lockdep_hardirqs_off(unsigned long ip) +{ + if (unlikely(!debug_locks)) + return; + + /* + * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep; + * they will restore the software state. This ensures the software + * state is consistent inside NMIs as well. + */ + if (in_nmi()) { + if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) + return; + } else if (__this_cpu_read(lockdep_recursion)) + return; + + /* + * So we're supposed to get called after you mask local IRQs, but for + * some reason the hardware doesn't quite think you did a proper job. + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return; + + if (lockdep_hardirqs_enabled()) { + struct irqtrace_events *trace = ¤t->irqtrace; + + /* + * We have done an ON -> OFF transition: + */ + __this_cpu_write(hardirqs_enabled, 0); + trace->hardirq_disable_ip = ip; + trace->hardirq_disable_event = ++trace->irq_events; + debug_atomic_inc(hardirqs_off_events); + } else { + debug_atomic_inc(redundant_hardirqs_off); + } +} +EXPORT_SYMBOL_GPL(lockdep_hardirqs_off); + +/* + * Softirqs will be enabled: + */ +void lockdep_softirqs_on(unsigned long ip) +{ + struct irqtrace_events *trace = ¤t->irqtrace; + + if (unlikely(!lockdep_enabled())) + return; + + /* + * We fancy IRQs being disabled here, see softirq.c, avoids + * funny state and nesting things. + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return; + + if (current->softirqs_enabled) { + debug_atomic_inc(redundant_softirqs_on); + return; + } + + lockdep_recursion_inc(); + /* + * We'll do an OFF -> ON transition: + */ + current->softirqs_enabled = 1; + trace->softirq_enable_ip = ip; + trace->softirq_enable_event = ++trace->irq_events; + debug_atomic_inc(softirqs_on_events); + /* + * We are going to turn softirqs on, so set the + * usage bit for all held locks, if hardirqs are + * enabled too: + */ + if (lockdep_hardirqs_enabled()) + mark_held_locks(current, LOCK_ENABLED_SOFTIRQ); + lockdep_recursion_finish(); +} + +/* + * Softirqs were disabled: + */ +void lockdep_softirqs_off(unsigned long ip) +{ + if (unlikely(!lockdep_enabled())) + return; + + /* + * We fancy IRQs being disabled here, see softirq.c + */ + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return; + + if (current->softirqs_enabled) { + struct irqtrace_events *trace = ¤t->irqtrace; + + /* + * We have done an ON -> OFF transition: + */ + current->softirqs_enabled = 0; + trace->softirq_disable_ip = ip; + trace->softirq_disable_event = ++trace->irq_events; + debug_atomic_inc(softirqs_off_events); + /* + * Whoops, we wanted softirqs off, so why aren't they? + */ + DEBUG_LOCKS_WARN_ON(!softirq_count()); + } else + debug_atomic_inc(redundant_softirqs_off); +} + +static int +mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) +{ + if (!check) + goto lock_used; + + /* + * If non-trylock use in a hardirq or softirq context, then + * mark the lock as used in these contexts: + */ + if (!hlock->trylock) { + if (hlock->read) { + if (lockdep_hardirq_context()) + if (!mark_lock(curr, hlock, + LOCK_USED_IN_HARDIRQ_READ)) + return 0; + if (curr->softirq_context) + if (!mark_lock(curr, hlock, + LOCK_USED_IN_SOFTIRQ_READ)) + return 0; + } else { + if (lockdep_hardirq_context()) + if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ)) + return 0; + if (curr->softirq_context) + if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ)) + return 0; + } + } + if (!hlock->hardirqs_off) { + if (hlock->read) { + if (!mark_lock(curr, hlock, + LOCK_ENABLED_HARDIRQ_READ)) + return 0; + if (curr->softirqs_enabled) + if (!mark_lock(curr, hlock, + LOCK_ENABLED_SOFTIRQ_READ)) + return 0; + } else { + if (!mark_lock(curr, hlock, + LOCK_ENABLED_HARDIRQ)) + return 0; + if (curr->softirqs_enabled) + if (!mark_lock(curr, hlock, + LOCK_ENABLED_SOFTIRQ)) + return 0; + } + } + +lock_used: + /* mark it as used: */ + if (!mark_lock(curr, hlock, LOCK_USED)) + return 0; + + return 1; +} + +static inline unsigned int task_irq_context(struct task_struct *task) +{ + return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() + + LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context; +} + +static int separate_irq_context(struct task_struct *curr, + struct held_lock *hlock) +{ + unsigned int depth = curr->lockdep_depth; + + /* + * Keep track of points where we cross into an interrupt context: + */ + if (depth) { + struct held_lock *prev_hlock; + + prev_hlock = curr->held_locks + depth-1; + /* + * If we cross into another context, reset the + * hash key (this also prevents the checking and the + * adding of the dependency to 'prev'): + */ + if (prev_hlock->irq_context != hlock->irq_context) + return 1; + } + return 0; +} + +/* + * Mark a lock with a usage bit, and validate the state transition: + */ +static int mark_lock(struct task_struct *curr, struct held_lock *this, + enum lock_usage_bit new_bit) +{ + unsigned int new_mask, ret = 1; + + if (new_bit >= LOCK_USAGE_STATES) { + DEBUG_LOCKS_WARN_ON(1); + return 0; + } + + if (new_bit == LOCK_USED && this->read) + new_bit = LOCK_USED_READ; + + new_mask = 1 << new_bit; + + /* + * If already set then do not dirty the cacheline, + * nor do any checks: + */ + if (likely(hlock_class(this)->usage_mask & new_mask)) + return 1; + + if (!graph_lock()) + return 0; + /* + * Make sure we didn't race: + */ + if (unlikely(hlock_class(this)->usage_mask & new_mask)) + goto unlock; + + if (!hlock_class(this)->usage_mask) + debug_atomic_dec(nr_unused_locks); + + hlock_class(this)->usage_mask |= new_mask; + + if (new_bit < LOCK_TRACE_STATES) { + if (!(hlock_class(this)->usage_traces[new_bit] = save_trace())) + return 0; + } + + if (new_bit < LOCK_USED) { + ret = mark_lock_irq(curr, this, new_bit); + if (!ret) + return 0; + } + +unlock: + graph_unlock(); + + /* + * We must printk outside of the graph_lock: + */ + if (ret == 2) { + printk("\nmarked lock as {%s}:\n", usage_str[new_bit]); + print_lock(this); + print_irqtrace_events(curr); + dump_stack(); + } + + return ret; +} + +static inline short task_wait_context(struct task_struct *curr) +{ + /* + * Set appropriate wait type for the context; for IRQs we have to take + * into account force_irqthread as that is implied by PREEMPT_RT. + */ + if (lockdep_hardirq_context()) { + /* + * Check if force_irqthreads will run us threaded. + */ + if (curr->hardirq_threaded || curr->irq_config) + return LD_WAIT_CONFIG; + + return LD_WAIT_SPIN; + } else if (curr->softirq_context) { + /* + * Softirqs are always threaded. + */ + return LD_WAIT_CONFIG; + } + + return LD_WAIT_MAX; +} + +static int +print_lock_invalid_wait_context(struct task_struct *curr, + struct held_lock *hlock) +{ + short curr_inner; + + if (!debug_locks_off()) + return 0; + if (debug_locks_silent) + return 0; + + pr_warn("\n"); + pr_warn("=============================\n"); + pr_warn("[ BUG: Invalid wait context ]\n"); + print_kernel_ident(); + pr_warn("-----------------------------\n"); + + pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr)); + print_lock(hlock); + + pr_warn("other info that might help us debug this:\n"); + + curr_inner = task_wait_context(curr); + pr_warn("context-{%d:%d}\n", curr_inner, curr_inner); + + lockdep_print_held_locks(curr); + + pr_warn("stack backtrace:\n"); + dump_stack(); + + return 0; +} + +/* + * Verify the wait_type context. + * + * This check validates we take locks in the right wait-type order; that is it + * ensures that we do not take mutexes inside spinlocks and do not attempt to + * acquire spinlocks inside raw_spinlocks and the sort. + * + * The entire thing is slightly more complex because of RCU, RCU is a lock that + * can be taken from (pretty much) any context but also has constraints. + * However when taken in a stricter environment the RCU lock does not loosen + * the constraints. + * + * Therefore we must look for the strictest environment in the lock stack and + * compare that to the lock we're trying to acquire. + */ +static int check_wait_context(struct task_struct *curr, struct held_lock *next) +{ + u8 next_inner = hlock_class(next)->wait_type_inner; + u8 next_outer = hlock_class(next)->wait_type_outer; + u8 curr_inner; + int depth; + + if (!next_inner || next->trylock) + return 0; + + if (!next_outer) + next_outer = next_inner; + + /* + * Find start of current irq_context.. + */ + for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) { + struct held_lock *prev = curr->held_locks + depth; + if (prev->irq_context != next->irq_context) + break; + } + depth++; + + curr_inner = task_wait_context(curr); + + for (; depth < curr->lockdep_depth; depth++) { + struct held_lock *prev = curr->held_locks + depth; + u8 prev_inner = hlock_class(prev)->wait_type_inner; + + if (prev_inner) { + /* + * We can have a bigger inner than a previous one + * when outer is smaller than inner, as with RCU. + * + * Also due to trylocks. + */ + curr_inner = min(curr_inner, prev_inner); + } + } + + if (next_outer > curr_inner) + return print_lock_invalid_wait_context(curr, next); + + return 0; +} + +#else /* CONFIG_PROVE_LOCKING */ + +static inline int +mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) +{ + return 1; +} + +static inline unsigned int task_irq_context(struct task_struct *task) +{ + return 0; +} + +static inline int separate_irq_context(struct task_struct *curr, + struct held_lock *hlock) +{ + return 0; +} + +static inline int check_wait_context(struct task_struct *curr, + struct held_lock *next) +{ + return 0; +} + +#endif /* CONFIG_PROVE_LOCKING */ + +/* + * Initialize a lock instance's lock-class mapping info: + */ +void lockdep_init_map_type(struct lockdep_map *lock, const char *name, + struct lock_class_key *key, int subclass, + u8 inner, u8 outer, u8 lock_type) +{ + int i; + + for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++) + lock->class_cache[i] = NULL; + +#ifdef CONFIG_LOCK_STAT + lock->cpu = raw_smp_processor_id(); +#endif + + /* + * Can't be having no nameless bastards around this place! + */ + if (DEBUG_LOCKS_WARN_ON(!name)) { + lock->name = "NULL"; + return; + } + + lock->name = name; + + lock->wait_type_outer = outer; + lock->wait_type_inner = inner; + lock->lock_type = lock_type; + + /* + * No key, no joy, we need to hash something. + */ + if (DEBUG_LOCKS_WARN_ON(!key)) + return; + /* + * Sanity check, the lock-class key must either have been allocated + * statically or must have been registered as a dynamic key. + */ + if (!static_obj(key) && !is_dynamic_key(key)) { + if (debug_locks) + printk(KERN_ERR "BUG: key %px has not been registered!\n", key); + DEBUG_LOCKS_WARN_ON(1); + return; + } + lock->key = key; + + if (unlikely(!debug_locks)) + return; + + if (subclass) { + unsigned long flags; + + if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + lockdep_recursion_inc(); + register_lock_class(lock, subclass, 1); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); + } +} +EXPORT_SYMBOL_GPL(lockdep_init_map_type); + +struct lock_class_key __lockdep_no_validate__; +EXPORT_SYMBOL_GPL(__lockdep_no_validate__); + +static void +print_lock_nested_lock_not_held(struct task_struct *curr, + struct held_lock *hlock) +{ + if (!debug_locks_off()) + return; + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("==================================\n"); + pr_warn("WARNING: Nested lock was not taken\n"); + print_kernel_ident(); + pr_warn("----------------------------------\n"); + + pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr)); + print_lock(hlock); + + pr_warn("\nbut this task is not holding:\n"); + pr_warn("%s\n", hlock->nest_lock->name); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); + + pr_warn("\nother info that might help us debug this:\n"); + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +static int __lock_is_held(const struct lockdep_map *lock, int read); + +/* + * This gets called for every mutex_lock*()/spin_lock*() operation. + * We maintain the dependency maps and validate the locking attempt: + * + * The callers must make sure that IRQs are disabled before calling it, + * otherwise we could get an interrupt which would want to take locks, + * which would end up in lockdep again. + */ +static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, + int trylock, int read, int check, int hardirqs_off, + struct lockdep_map *nest_lock, unsigned long ip, + int references, int pin_count) +{ + struct task_struct *curr = current; + struct lock_class *class = NULL; + struct held_lock *hlock; + unsigned int depth; + int chain_head = 0; + int class_idx; + u64 chain_key; + + if (unlikely(!debug_locks)) + return 0; + + if (!prove_locking || lock->key == &__lockdep_no_validate__) + check = 0; + + if (subclass < NR_LOCKDEP_CACHING_CLASSES) + class = lock->class_cache[subclass]; + /* + * Not cached? + */ + if (unlikely(!class)) { + class = register_lock_class(lock, subclass, 0); + if (!class) + return 0; + } + + debug_class_ops_inc(class); + + if (very_verbose(class)) { + printk("\nacquire class [%px] %s", class->key, class->name); + if (class->name_version > 1) + printk(KERN_CONT "#%d", class->name_version); + printk(KERN_CONT "\n"); + dump_stack(); + } + + /* + * Add the lock to the list of currently held locks. + * (we dont increase the depth just yet, up until the + * dependency checks are done) + */ + depth = curr->lockdep_depth; + /* + * Ran out of static storage for our per-task lock stack again have we? + */ + if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)) + return 0; + + class_idx = class - lock_classes; + + if (depth) { /* we're holding locks */ + hlock = curr->held_locks + depth - 1; + if (hlock->class_idx == class_idx && nest_lock) { + if (!references) + references++; + + if (!hlock->references) + hlock->references++; + + hlock->references += references; + + /* Overflow */ + if (DEBUG_LOCKS_WARN_ON(hlock->references < references)) + return 0; + + return 2; + } + } + + hlock = curr->held_locks + depth; + /* + * Plain impossible, we just registered it and checked it weren't no + * NULL like.. I bet this mushroom I ate was good! + */ + if (DEBUG_LOCKS_WARN_ON(!class)) + return 0; + hlock->class_idx = class_idx; + hlock->acquire_ip = ip; + hlock->instance = lock; + hlock->nest_lock = nest_lock; + hlock->irq_context = task_irq_context(curr); + hlock->trylock = trylock; + hlock->read = read; + hlock->check = check; + hlock->hardirqs_off = !!hardirqs_off; + hlock->references = references; +#ifdef CONFIG_LOCK_STAT + hlock->waittime_stamp = 0; + hlock->holdtime_stamp = lockstat_clock(); +#endif + hlock->pin_count = pin_count; + + if (check_wait_context(curr, hlock)) + return 0; + + /* Initialize the lock usage bit */ + if (!mark_usage(curr, hlock, check)) + return 0; + + /* + * Calculate the chain hash: it's the combined hash of all the + * lock keys along the dependency chain. We save the hash value + * at every step so that we can get the current hash easily + * after unlock. The chain hash is then used to cache dependency + * results. + * + * The 'key ID' is what is the most compact key value to drive + * the hash, not class->key. + */ + /* + * Whoops, we did it again.. class_idx is invalid. + */ + if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use))) + return 0; + + chain_key = curr->curr_chain_key; + if (!depth) { + /* + * How can we have a chain hash when we ain't got no keys?! + */ + if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY)) + return 0; + chain_head = 1; + } + + hlock->prev_chain_key = chain_key; + if (separate_irq_context(curr, hlock)) { + chain_key = INITIAL_CHAIN_KEY; + chain_head = 1; + } + chain_key = iterate_chain_key(chain_key, hlock_id(hlock)); + + if (nest_lock && !__lock_is_held(nest_lock, -1)) { + print_lock_nested_lock_not_held(curr, hlock); + return 0; + } + + if (!debug_locks_silent) { + WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key); + WARN_ON_ONCE(!hlock_class(hlock)->key); + } + + if (!validate_chain(curr, hlock, chain_head, chain_key)) + return 0; + + curr->curr_chain_key = chain_key; + curr->lockdep_depth++; + check_chain_key(curr); +#ifdef CONFIG_DEBUG_LOCKDEP + if (unlikely(!debug_locks)) + return 0; +#endif + if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { + debug_locks_off(); + print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!"); + printk(KERN_DEBUG "depth: %i max: %lu!\n", + curr->lockdep_depth, MAX_LOCK_DEPTH); + + lockdep_print_held_locks(current); + debug_show_all_locks(); + dump_stack(); + + return 0; + } + + if (unlikely(curr->lockdep_depth > max_lockdep_depth)) + max_lockdep_depth = curr->lockdep_depth; + + return 1; +} + +static void print_unlock_imbalance_bug(struct task_struct *curr, + struct lockdep_map *lock, + unsigned long ip) +{ + if (!debug_locks_off()) + return; + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("=====================================\n"); + pr_warn("WARNING: bad unlock balance detected!\n"); + print_kernel_ident(); + pr_warn("-------------------------------------\n"); + pr_warn("%s/%d is trying to release lock (", + curr->comm, task_pid_nr(curr)); + print_lockdep_cache(lock); + pr_cont(") at:\n"); + print_ip_sym(KERN_WARNING, ip); + pr_warn("but there are no more locks to release!\n"); + pr_warn("\nother info that might help us debug this:\n"); + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +static noinstr int match_held_lock(const struct held_lock *hlock, + const struct lockdep_map *lock) +{ + if (hlock->instance == lock) + return 1; + + if (hlock->references) { + const struct lock_class *class = lock->class_cache[0]; + + if (!class) + class = look_up_lock_class(lock, 0); + + /* + * If look_up_lock_class() failed to find a class, we're trying + * to test if we hold a lock that has never yet been acquired. + * Clearly if the lock hasn't been acquired _ever_, we're not + * holding it either, so report failure. + */ + if (!class) + return 0; + + /* + * References, but not a lock we're actually ref-counting? + * State got messed up, follow the sites that change ->references + * and try to make sense of it. + */ + if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock)) + return 0; + + if (hlock->class_idx == class - lock_classes) + return 1; + } + + return 0; +} + +/* @depth must not be zero */ +static struct held_lock *find_held_lock(struct task_struct *curr, + struct lockdep_map *lock, + unsigned int depth, int *idx) +{ + struct held_lock *ret, *hlock, *prev_hlock; + int i; + + i = depth - 1; + hlock = curr->held_locks + i; + ret = hlock; + if (match_held_lock(hlock, lock)) + goto out; + + ret = NULL; + for (i--, prev_hlock = hlock--; + i >= 0; + i--, prev_hlock = hlock--) { + /* + * We must not cross into another context: + */ + if (prev_hlock->irq_context != hlock->irq_context) { + ret = NULL; + break; + } + if (match_held_lock(hlock, lock)) { + ret = hlock; + break; + } + } + +out: + *idx = i; + return ret; +} + +static int reacquire_held_locks(struct task_struct *curr, unsigned int depth, + int idx, unsigned int *merged) +{ + struct held_lock *hlock; + int first_idx = idx; + + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) + return 0; + + for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) { + switch (__lock_acquire(hlock->instance, + hlock_class(hlock)->subclass, + hlock->trylock, + hlock->read, hlock->check, + hlock->hardirqs_off, + hlock->nest_lock, hlock->acquire_ip, + hlock->references, hlock->pin_count)) { + case 0: + return 1; + case 1: + break; + case 2: + *merged += (idx == first_idx); + break; + default: + WARN_ON(1); + return 0; + } + } + return 0; +} + +static int +__lock_set_class(struct lockdep_map *lock, const char *name, + struct lock_class_key *key, unsigned int subclass, + unsigned long ip) +{ + struct task_struct *curr = current; + unsigned int depth, merged = 0; + struct held_lock *hlock; + struct lock_class *class; + int i; + + if (unlikely(!debug_locks)) + return 0; + + depth = curr->lockdep_depth; + /* + * This function is about (re)setting the class of a held lock, + * yet we're not actually holding any locks. Naughty user! + */ + if (DEBUG_LOCKS_WARN_ON(!depth)) + return 0; + + hlock = find_held_lock(curr, lock, depth, &i); + if (!hlock) { + print_unlock_imbalance_bug(curr, lock, ip); + return 0; + } + + lockdep_init_map_type(lock, name, key, 0, + lock->wait_type_inner, + lock->wait_type_outer, + lock->lock_type); + class = register_lock_class(lock, subclass, 0); + hlock->class_idx = class - lock_classes; + + curr->lockdep_depth = i; + curr->curr_chain_key = hlock->prev_chain_key; + + if (reacquire_held_locks(curr, depth, i, &merged)) + return 0; + + /* + * I took it apart and put it back together again, except now I have + * these 'spare' parts.. where shall I put them. + */ + if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged)) + return 0; + return 1; +} + +static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr = current; + unsigned int depth, merged = 0; + struct held_lock *hlock; + int i; + + if (unlikely(!debug_locks)) + return 0; + + depth = curr->lockdep_depth; + /* + * This function is about (re)setting the class of a held lock, + * yet we're not actually holding any locks. Naughty user! + */ + if (DEBUG_LOCKS_WARN_ON(!depth)) + return 0; + + hlock = find_held_lock(curr, lock, depth, &i); + if (!hlock) { + print_unlock_imbalance_bug(curr, lock, ip); + return 0; + } + + curr->lockdep_depth = i; + curr->curr_chain_key = hlock->prev_chain_key; + + WARN(hlock->read, "downgrading a read lock"); + hlock->read = 1; + hlock->acquire_ip = ip; + + if (reacquire_held_locks(curr, depth, i, &merged)) + return 0; + + /* Merging can't happen with unchanged classes.. */ + if (DEBUG_LOCKS_WARN_ON(merged)) + return 0; + + /* + * I took it apart and put it back together again, except now I have + * these 'spare' parts.. where shall I put them. + */ + if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth)) + return 0; + + return 1; +} + +/* + * Remove the lock from the list of currently held locks - this gets + * called on mutex_unlock()/spin_unlock*() (or on a failed + * mutex_lock_interruptible()). + */ +static int +__lock_release(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr = current; + unsigned int depth, merged = 1; + struct held_lock *hlock; + int i; + + if (unlikely(!debug_locks)) + return 0; + + depth = curr->lockdep_depth; + /* + * So we're all set to release this lock.. wait what lock? We don't + * own any locks, you've been drinking again? + */ + if (depth <= 0) { + print_unlock_imbalance_bug(curr, lock, ip); + return 0; + } + + /* + * Check whether the lock exists in the current stack + * of held locks: + */ + hlock = find_held_lock(curr, lock, depth, &i); + if (!hlock) { + print_unlock_imbalance_bug(curr, lock, ip); + return 0; + } + + if (hlock->instance == lock) + lock_release_holdtime(hlock); + + WARN(hlock->pin_count, "releasing a pinned lock\n"); + + if (hlock->references) { + hlock->references--; + if (hlock->references) { + /* + * We had, and after removing one, still have + * references, the current lock stack is still + * valid. We're done! + */ + return 1; + } + } + + /* + * We have the right lock to unlock, 'hlock' points to it. + * Now we remove it from the stack, and add back the other + * entries (if any), recalculating the hash along the way: + */ + + curr->lockdep_depth = i; + curr->curr_chain_key = hlock->prev_chain_key; + + /* + * The most likely case is when the unlock is on the innermost + * lock. In this case, we are done! + */ + if (i == depth-1) + return 1; + + if (reacquire_held_locks(curr, depth, i + 1, &merged)) + return 0; + + /* + * We had N bottles of beer on the wall, we drank one, but now + * there's not N-1 bottles of beer left on the wall... + * Pouring two of the bottles together is acceptable. + */ + DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged); + + /* + * Since reacquire_held_locks() would have called check_chain_key() + * indirectly via __lock_acquire(), we don't need to do it again + * on return. + */ + return 0; +} + +static __always_inline +int __lock_is_held(const struct lockdep_map *lock, int read) +{ + struct task_struct *curr = current; + int i; + + for (i = 0; i < curr->lockdep_depth; i++) { + struct held_lock *hlock = curr->held_locks + i; + + if (match_held_lock(hlock, lock)) { + if (read == -1 || !!hlock->read == read) + return LOCK_STATE_HELD; + + return LOCK_STATE_NOT_HELD; + } + } + + return LOCK_STATE_NOT_HELD; +} + +static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock) +{ + struct pin_cookie cookie = NIL_COOKIE; + struct task_struct *curr = current; + int i; + + if (unlikely(!debug_locks)) + return cookie; + + for (i = 0; i < curr->lockdep_depth; i++) { + struct held_lock *hlock = curr->held_locks + i; + + if (match_held_lock(hlock, lock)) { + /* + * Grab 16bits of randomness; this is sufficient to not + * be guessable and still allows some pin nesting in + * our u32 pin_count. + */ + cookie.val = 1 + (sched_clock() & 0xffff); + hlock->pin_count += cookie.val; + return cookie; + } + } + + WARN(1, "pinning an unheld lock\n"); + return cookie; +} + +static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie) +{ + struct task_struct *curr = current; + int i; + + if (unlikely(!debug_locks)) + return; + + for (i = 0; i < curr->lockdep_depth; i++) { + struct held_lock *hlock = curr->held_locks + i; + + if (match_held_lock(hlock, lock)) { + hlock->pin_count += cookie.val; + return; + } + } + + WARN(1, "pinning an unheld lock\n"); +} + +static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie) +{ + struct task_struct *curr = current; + int i; + + if (unlikely(!debug_locks)) + return; + + for (i = 0; i < curr->lockdep_depth; i++) { + struct held_lock *hlock = curr->held_locks + i; + + if (match_held_lock(hlock, lock)) { + if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n")) + return; + + hlock->pin_count -= cookie.val; + + if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n")) + hlock->pin_count = 0; + + return; + } + } + + WARN(1, "unpinning an unheld lock\n"); +} + +/* + * Check whether we follow the irq-flags state precisely: + */ +static noinstr void check_flags(unsigned long flags) +{ +#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) + if (!debug_locks) + return; + + /* Get the warning out.. */ + instrumentation_begin(); + + if (irqs_disabled_flags(flags)) { + if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) { + printk("possible reason: unannotated irqs-off.\n"); + } + } else { + if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) { + printk("possible reason: unannotated irqs-on.\n"); + } + } + +#ifndef CONFIG_PREEMPT_RT + /* + * We dont accurately track softirq state in e.g. + * hardirq contexts (such as on 4KSTACKS), so only + * check if not in hardirq contexts: + */ + if (!hardirq_count()) { + if (softirq_count()) { + /* like the above, but with softirqs */ + DEBUG_LOCKS_WARN_ON(current->softirqs_enabled); + } else { + /* lick the above, does it taste good? */ + DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled); + } + } +#endif + + if (!debug_locks) + print_irqtrace_events(current); + + instrumentation_end(); +#endif +} + +void lock_set_class(struct lockdep_map *lock, const char *name, + struct lock_class_key *key, unsigned int subclass, + unsigned long ip) +{ + unsigned long flags; + + if (unlikely(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + lockdep_recursion_inc(); + check_flags(flags); + if (__lock_set_class(lock, name, key, subclass, ip)) + check_chain_key(current); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_set_class); + +void lock_downgrade(struct lockdep_map *lock, unsigned long ip) +{ + unsigned long flags; + + if (unlikely(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + lockdep_recursion_inc(); + check_flags(flags); + if (__lock_downgrade(lock, ip)) + check_chain_key(current); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_downgrade); + +/* NMI context !!! */ +static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass) +{ +#ifdef CONFIG_PROVE_LOCKING + struct lock_class *class = look_up_lock_class(lock, subclass); + unsigned long mask = LOCKF_USED; + + /* if it doesn't have a class (yet), it certainly hasn't been used yet */ + if (!class) + return; + + /* + * READ locks only conflict with USED, such that if we only ever use + * READ locks, there is no deadlock possible -- RCU. + */ + if (!hlock->read) + mask |= LOCKF_USED_READ; + + if (!(class->usage_mask & mask)) + return; + + hlock->class_idx = class - lock_classes; + + print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES); +#endif +} + +static bool lockdep_nmi(void) +{ + if (raw_cpu_read(lockdep_recursion)) + return false; + + if (!in_nmi()) + return false; + + return true; +} + +/* + * read_lock() is recursive if: + * 1. We force lockdep think this way in selftests or + * 2. The implementation is not queued read/write lock or + * 3. The locker is at an in_interrupt() context. + */ +bool read_lock_is_recursive(void) +{ + return force_read_lock_recursive || + !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) || + in_interrupt(); +} +EXPORT_SYMBOL_GPL(read_lock_is_recursive); + +/* + * We are not always called with irqs disabled - do that here, + * and also avoid lockdep recursion: + */ +void lock_acquire(struct lockdep_map *lock, unsigned int subclass, + int trylock, int read, int check, + struct lockdep_map *nest_lock, unsigned long ip) +{ + unsigned long flags; + + trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); + + if (!debug_locks) + return; + + if (unlikely(!lockdep_enabled())) { + /* XXX allow trylock from NMI ?!? */ + if (lockdep_nmi() && !trylock) { + struct held_lock hlock; + + hlock.acquire_ip = ip; + hlock.instance = lock; + hlock.nest_lock = nest_lock; + hlock.irq_context = 2; // XXX + hlock.trylock = trylock; + hlock.read = read; + hlock.check = check; + hlock.hardirqs_off = true; + hlock.references = 0; + + verify_lock_unused(lock, &hlock, subclass); + } + return; + } + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + __lock_acquire(lock, subclass, trylock, read, check, + irqs_disabled_flags(flags), nest_lock, ip, 0, 0); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_acquire); + +void lock_release(struct lockdep_map *lock, unsigned long ip) +{ + unsigned long flags; + + trace_lock_release(lock, ip); + + if (unlikely(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + if (__lock_release(lock, ip)) + check_chain_key(current); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_release); + +noinstr int lock_is_held_type(const struct lockdep_map *lock, int read) +{ + unsigned long flags; + int ret = LOCK_STATE_NOT_HELD; + + /* + * Avoid false negative lockdep_assert_held() and + * lockdep_assert_not_held(). + */ + if (unlikely(!lockdep_enabled())) + return LOCK_STATE_UNKNOWN; + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + ret = __lock_is_held(lock, read); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); + + return ret; +} +EXPORT_SYMBOL_GPL(lock_is_held_type); +NOKPROBE_SYMBOL(lock_is_held_type); + +struct pin_cookie lock_pin_lock(struct lockdep_map *lock) +{ + struct pin_cookie cookie = NIL_COOKIE; + unsigned long flags; + + if (unlikely(!lockdep_enabled())) + return cookie; + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + cookie = __lock_pin_lock(lock); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); + + return cookie; +} +EXPORT_SYMBOL_GPL(lock_pin_lock); + +void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie) +{ + unsigned long flags; + + if (unlikely(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + __lock_repin_lock(lock, cookie); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_repin_lock); + +void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie) +{ + unsigned long flags; + + if (unlikely(!lockdep_enabled())) + return; + + raw_local_irq_save(flags); + check_flags(flags); + + lockdep_recursion_inc(); + __lock_unpin_lock(lock, cookie); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_unpin_lock); + +#ifdef CONFIG_LOCK_STAT +static void print_lock_contention_bug(struct task_struct *curr, + struct lockdep_map *lock, + unsigned long ip) +{ + if (!debug_locks_off()) + return; + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("=================================\n"); + pr_warn("WARNING: bad contention detected!\n"); + print_kernel_ident(); + pr_warn("---------------------------------\n"); + pr_warn("%s/%d is trying to contend lock (", + curr->comm, task_pid_nr(curr)); + print_lockdep_cache(lock); + pr_cont(") at:\n"); + print_ip_sym(KERN_WARNING, ip); + pr_warn("but there are no locks held!\n"); + pr_warn("\nother info that might help us debug this:\n"); + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +static void +__lock_contended(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr = current; + struct held_lock *hlock; + struct lock_class_stats *stats; + unsigned int depth; + int i, contention_point, contending_point; + + depth = curr->lockdep_depth; + /* + * Whee, we contended on this lock, except it seems we're not + * actually trying to acquire anything much at all.. + */ + if (DEBUG_LOCKS_WARN_ON(!depth)) + return; + + hlock = find_held_lock(curr, lock, depth, &i); + if (!hlock) { + print_lock_contention_bug(curr, lock, ip); + return; + } + + if (hlock->instance != lock) + return; + + hlock->waittime_stamp = lockstat_clock(); + + contention_point = lock_point(hlock_class(hlock)->contention_point, ip); + contending_point = lock_point(hlock_class(hlock)->contending_point, + lock->ip); + + stats = get_lock_stats(hlock_class(hlock)); + if (contention_point < LOCKSTAT_POINTS) + stats->contention_point[contention_point]++; + if (contending_point < LOCKSTAT_POINTS) + stats->contending_point[contending_point]++; + if (lock->cpu != smp_processor_id()) + stats->bounces[bounce_contended + !!hlock->read]++; +} + +static void +__lock_acquired(struct lockdep_map *lock, unsigned long ip) +{ + struct task_struct *curr = current; + struct held_lock *hlock; + struct lock_class_stats *stats; + unsigned int depth; + u64 now, waittime = 0; + int i, cpu; + + depth = curr->lockdep_depth; + /* + * Yay, we acquired ownership of this lock we didn't try to + * acquire, how the heck did that happen? + */ + if (DEBUG_LOCKS_WARN_ON(!depth)) + return; + + hlock = find_held_lock(curr, lock, depth, &i); + if (!hlock) { + print_lock_contention_bug(curr, lock, _RET_IP_); + return; + } + + if (hlock->instance != lock) + return; + + cpu = smp_processor_id(); + if (hlock->waittime_stamp) { + now = lockstat_clock(); + waittime = now - hlock->waittime_stamp; + hlock->holdtime_stamp = now; + } + + stats = get_lock_stats(hlock_class(hlock)); + if (waittime) { + if (hlock->read) + lock_time_inc(&stats->read_waittime, waittime); + else + lock_time_inc(&stats->write_waittime, waittime); + } + if (lock->cpu != cpu) + stats->bounces[bounce_acquired + !!hlock->read]++; + + lock->cpu = cpu; + lock->ip = ip; +} + +void lock_contended(struct lockdep_map *lock, unsigned long ip) +{ + unsigned long flags; + + trace_lock_contended(lock, ip); + + if (unlikely(!lock_stat || !lockdep_enabled())) + return; + + raw_local_irq_save(flags); + check_flags(flags); + lockdep_recursion_inc(); + __lock_contended(lock, ip); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_contended); + +void lock_acquired(struct lockdep_map *lock, unsigned long ip) +{ + unsigned long flags; + + trace_lock_acquired(lock, ip); + + if (unlikely(!lock_stat || !lockdep_enabled())) + return; + + raw_local_irq_save(flags); + check_flags(flags); + lockdep_recursion_inc(); + __lock_acquired(lock, ip); + lockdep_recursion_finish(); + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(lock_acquired); +#endif + +/* + * Used by the testsuite, sanitize the validator state + * after a simulated failure: + */ + +void lockdep_reset(void) +{ + unsigned long flags; + int i; + + raw_local_irq_save(flags); + lockdep_init_task(current); + memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock)); + nr_hardirq_chains = 0; + nr_softirq_chains = 0; + nr_process_chains = 0; + debug_locks = 1; + for (i = 0; i < CHAINHASH_SIZE; i++) + INIT_HLIST_HEAD(chainhash_table + i); + raw_local_irq_restore(flags); +} + +/* Remove a class from a lock chain. Must be called with the graph lock held. */ +static void remove_class_from_lock_chain(struct pending_free *pf, + struct lock_chain *chain, + struct lock_class *class) +{ +#ifdef CONFIG_PROVE_LOCKING + int i; + + for (i = chain->base; i < chain->base + chain->depth; i++) { + if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes) + continue; + /* + * Each lock class occurs at most once in a lock chain so once + * we found a match we can break out of this loop. + */ + goto free_lock_chain; + } + /* Since the chain has not been modified, return. */ + return; + +free_lock_chain: + free_chain_hlocks(chain->base, chain->depth); + /* Overwrite the chain key for concurrent RCU readers. */ + WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY); + dec_chains(chain->irq_context); + + /* + * Note: calling hlist_del_rcu() from inside a + * hlist_for_each_entry_rcu() loop is safe. + */ + hlist_del_rcu(&chain->entry); + __set_bit(chain - lock_chains, pf->lock_chains_being_freed); + nr_zapped_lock_chains++; +#endif +} + +/* Must be called with the graph lock held. */ +static void remove_class_from_lock_chains(struct pending_free *pf, + struct lock_class *class) +{ + struct lock_chain *chain; + struct hlist_head *head; + int i; + + for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) { + head = chainhash_table + i; + hlist_for_each_entry_rcu(chain, head, entry) { + remove_class_from_lock_chain(pf, chain, class); + } + } +} + +/* + * Remove all references to a lock class. The caller must hold the graph lock. + */ +static void zap_class(struct pending_free *pf, struct lock_class *class) +{ + struct lock_list *entry; + int i; + + WARN_ON_ONCE(!class->key); + + /* + * Remove all dependencies this lock is + * involved in: + */ + for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { + entry = list_entries + i; + if (entry->class != class && entry->links_to != class) + continue; + __clear_bit(i, list_entries_in_use); + nr_list_entries--; + list_del_rcu(&entry->entry); + } + if (list_empty(&class->locks_after) && + list_empty(&class->locks_before)) { + list_move_tail(&class->lock_entry, &pf->zapped); + hlist_del_rcu(&class->hash_entry); + WRITE_ONCE(class->key, NULL); + WRITE_ONCE(class->name, NULL); + nr_lock_classes--; + __clear_bit(class - lock_classes, lock_classes_in_use); + if (class - lock_classes == max_lock_class_idx) + max_lock_class_idx--; + } else { + WARN_ONCE(true, "%s() failed for class %s\n", __func__, + class->name); + } + + remove_class_from_lock_chains(pf, class); + nr_zapped_classes++; +} + +static void reinit_class(struct lock_class *class) +{ + WARN_ON_ONCE(!class->lock_entry.next); + WARN_ON_ONCE(!list_empty(&class->locks_after)); + WARN_ON_ONCE(!list_empty(&class->locks_before)); + memset_startat(class, 0, key); + WARN_ON_ONCE(!class->lock_entry.next); + WARN_ON_ONCE(!list_empty(&class->locks_after)); + WARN_ON_ONCE(!list_empty(&class->locks_before)); +} + +static inline int within(const void *addr, void *start, unsigned long size) +{ + return addr >= start && addr < start + size; +} + +static bool inside_selftest(void) +{ + return current == lockdep_selftest_task_struct; +} + +/* The caller must hold the graph lock. */ +static struct pending_free *get_pending_free(void) +{ + return delayed_free.pf + delayed_free.index; +} + +static void free_zapped_rcu(struct rcu_head *cb); + +/* + * Schedule an RCU callback if no RCU callback is pending. Must be called with + * the graph lock held. + */ +static void call_rcu_zapped(struct pending_free *pf) +{ + WARN_ON_ONCE(inside_selftest()); + + if (list_empty(&pf->zapped)) + return; + + if (delayed_free.scheduled) + return; + + delayed_free.scheduled = true; + + WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf); + delayed_free.index ^= 1; + + call_rcu(&delayed_free.rcu_head, free_zapped_rcu); +} + +/* The caller must hold the graph lock. May be called from RCU context. */ +static void __free_zapped_classes(struct pending_free *pf) +{ + struct lock_class *class; + + check_data_structures(); + + list_for_each_entry(class, &pf->zapped, lock_entry) + reinit_class(class); + + list_splice_init(&pf->zapped, &free_lock_classes); + +#ifdef CONFIG_PROVE_LOCKING + bitmap_andnot(lock_chains_in_use, lock_chains_in_use, + pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains)); + bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains)); +#endif +} + +static void free_zapped_rcu(struct rcu_head *ch) +{ + struct pending_free *pf; + unsigned long flags; + + if (WARN_ON_ONCE(ch != &delayed_free.rcu_head)) + return; + + raw_local_irq_save(flags); + lockdep_lock(); + + /* closed head */ + pf = delayed_free.pf + (delayed_free.index ^ 1); + __free_zapped_classes(pf); + delayed_free.scheduled = false; + + /* + * If there's anything on the open list, close and start a new callback. + */ + call_rcu_zapped(delayed_free.pf + delayed_free.index); + + lockdep_unlock(); + raw_local_irq_restore(flags); +} + +/* + * Remove all lock classes from the class hash table and from the + * all_lock_classes list whose key or name is in the address range [start, + * start + size). Move these lock classes to the zapped_classes list. Must + * be called with the graph lock held. + */ +static void __lockdep_free_key_range(struct pending_free *pf, void *start, + unsigned long size) +{ + struct lock_class *class; + struct hlist_head *head; + int i; + + /* Unhash all classes that were created by a module. */ + for (i = 0; i < CLASSHASH_SIZE; i++) { + head = classhash_table + i; + hlist_for_each_entry_rcu(class, head, hash_entry) { + if (!within(class->key, start, size) && + !within(class->name, start, size)) + continue; + zap_class(pf, class); + } + } +} + +/* + * Used in module.c to remove lock classes from memory that is going to be + * freed; and possibly re-used by other modules. + * + * We will have had one synchronize_rcu() before getting here, so we're + * guaranteed nobody will look up these exact classes -- they're properly dead + * but still allocated. + */ +static void lockdep_free_key_range_reg(void *start, unsigned long size) +{ + struct pending_free *pf; + unsigned long flags; + + init_data_structures_once(); + + raw_local_irq_save(flags); + lockdep_lock(); + pf = get_pending_free(); + __lockdep_free_key_range(pf, start, size); + call_rcu_zapped(pf); + lockdep_unlock(); + raw_local_irq_restore(flags); + + /* + * Wait for any possible iterators from look_up_lock_class() to pass + * before continuing to free the memory they refer to. + */ + synchronize_rcu(); +} + +/* + * Free all lockdep keys in the range [start, start+size). Does not sleep. + * Ignores debug_locks. Must only be used by the lockdep selftests. + */ +static void lockdep_free_key_range_imm(void *start, unsigned long size) +{ + struct pending_free *pf = delayed_free.pf; + unsigned long flags; + + init_data_structures_once(); + + raw_local_irq_save(flags); + lockdep_lock(); + __lockdep_free_key_range(pf, start, size); + __free_zapped_classes(pf); + lockdep_unlock(); + raw_local_irq_restore(flags); +} + +void lockdep_free_key_range(void *start, unsigned long size) +{ + init_data_structures_once(); + + if (inside_selftest()) + lockdep_free_key_range_imm(start, size); + else + lockdep_free_key_range_reg(start, size); +} + +/* + * Check whether any element of the @lock->class_cache[] array refers to a + * registered lock class. The caller must hold either the graph lock or the + * RCU read lock. + */ +static bool lock_class_cache_is_registered(struct lockdep_map *lock) +{ + struct lock_class *class; + struct hlist_head *head; + int i, j; + + for (i = 0; i < CLASSHASH_SIZE; i++) { + head = classhash_table + i; + hlist_for_each_entry_rcu(class, head, hash_entry) { + for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++) + if (lock->class_cache[j] == class) + return true; + } + } + return false; +} + +/* The caller must hold the graph lock. Does not sleep. */ +static void __lockdep_reset_lock(struct pending_free *pf, + struct lockdep_map *lock) +{ + struct lock_class *class; + int j; + + /* + * Remove all classes this lock might have: + */ + for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) { + /* + * If the class exists we look it up and zap it: + */ + class = look_up_lock_class(lock, j); + if (class) + zap_class(pf, class); + } + /* + * Debug check: in the end all mapped classes should + * be gone. + */ + if (WARN_ON_ONCE(lock_class_cache_is_registered(lock))) + debug_locks_off(); +} + +/* + * Remove all information lockdep has about a lock if debug_locks == 1. Free + * released data structures from RCU context. + */ +static void lockdep_reset_lock_reg(struct lockdep_map *lock) +{ + struct pending_free *pf; + unsigned long flags; + int locked; + + raw_local_irq_save(flags); + locked = graph_lock(); + if (!locked) + goto out_irq; + + pf = get_pending_free(); + __lockdep_reset_lock(pf, lock); + call_rcu_zapped(pf); + + graph_unlock(); +out_irq: + raw_local_irq_restore(flags); +} + +/* + * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the + * lockdep selftests. + */ +static void lockdep_reset_lock_imm(struct lockdep_map *lock) +{ + struct pending_free *pf = delayed_free.pf; + unsigned long flags; + + raw_local_irq_save(flags); + lockdep_lock(); + __lockdep_reset_lock(pf, lock); + __free_zapped_classes(pf); + lockdep_unlock(); + raw_local_irq_restore(flags); +} + +void lockdep_reset_lock(struct lockdep_map *lock) +{ + init_data_structures_once(); + + if (inside_selftest()) + lockdep_reset_lock_imm(lock); + else + lockdep_reset_lock_reg(lock); +} + +/* + * Unregister a dynamically allocated key. + * + * Unlike lockdep_register_key(), a search is always done to find a matching + * key irrespective of debug_locks to avoid potential invalid access to freed + * memory in lock_class entry. + */ +void lockdep_unregister_key(struct lock_class_key *key) +{ + struct hlist_head *hash_head = keyhashentry(key); + struct lock_class_key *k; + struct pending_free *pf; + unsigned long flags; + bool found = false; + + might_sleep(); + + if (WARN_ON_ONCE(static_obj(key))) + return; + + raw_local_irq_save(flags); + lockdep_lock(); + + hlist_for_each_entry_rcu(k, hash_head, hash_entry) { + if (k == key) { + hlist_del_rcu(&k->hash_entry); + found = true; + break; + } + } + WARN_ON_ONCE(!found && debug_locks); + if (found) { + pf = get_pending_free(); + __lockdep_free_key_range(pf, key, 1); + call_rcu_zapped(pf); + } + lockdep_unlock(); + raw_local_irq_restore(flags); + + /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(lockdep_unregister_key); + +void __init lockdep_init(void) +{ + printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n"); + + printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES); + printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH); + printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS); + printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE); + printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES); + printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS); + printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE); + + printk(" memory used by lock dependency info: %zu kB\n", + (sizeof(lock_classes) + + sizeof(lock_classes_in_use) + + sizeof(classhash_table) + + sizeof(list_entries) + + sizeof(list_entries_in_use) + + sizeof(chainhash_table) + + sizeof(delayed_free) +#ifdef CONFIG_PROVE_LOCKING + + sizeof(lock_cq) + + sizeof(lock_chains) + + sizeof(lock_chains_in_use) + + sizeof(chain_hlocks) +#endif + ) / 1024 + ); + +#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) + printk(" memory used for stack traces: %zu kB\n", + (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024 + ); +#endif + + printk(" per task-struct memory footprint: %zu bytes\n", + sizeof(((struct task_struct *)NULL)->held_locks)); +} + +static void +print_freed_lock_bug(struct task_struct *curr, const void *mem_from, + const void *mem_to, struct held_lock *hlock) +{ + if (!debug_locks_off()) + return; + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("=========================\n"); + pr_warn("WARNING: held lock freed!\n"); + print_kernel_ident(); + pr_warn("-------------------------\n"); + pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n", + curr->comm, task_pid_nr(curr), mem_from, mem_to-1); + print_lock(hlock); + lockdep_print_held_locks(curr); + + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +static inline int not_in_range(const void* mem_from, unsigned long mem_len, + const void* lock_from, unsigned long lock_len) +{ + return lock_from + lock_len <= mem_from || + mem_from + mem_len <= lock_from; +} + +/* + * Called when kernel memory is freed (or unmapped), or if a lock + * is destroyed or reinitialized - this code checks whether there is + * any held lock in the memory range of <from> to <to>: + */ +void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len) +{ + struct task_struct *curr = current; + struct held_lock *hlock; + unsigned long flags; + int i; + + if (unlikely(!debug_locks)) + return; + + raw_local_irq_save(flags); + for (i = 0; i < curr->lockdep_depth; i++) { + hlock = curr->held_locks + i; + + if (not_in_range(mem_from, mem_len, hlock->instance, + sizeof(*hlock->instance))) + continue; + + print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock); + break; + } + raw_local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(debug_check_no_locks_freed); + +static void print_held_locks_bug(void) +{ + if (!debug_locks_off()) + return; + if (debug_locks_silent) + return; + + pr_warn("\n"); + pr_warn("====================================\n"); + pr_warn("WARNING: %s/%d still has locks held!\n", + current->comm, task_pid_nr(current)); + print_kernel_ident(); + pr_warn("------------------------------------\n"); + lockdep_print_held_locks(current); + pr_warn("\nstack backtrace:\n"); + dump_stack(); +} + +void debug_check_no_locks_held(void) +{ + if (unlikely(current->lockdep_depth > 0)) + print_held_locks_bug(); +} +EXPORT_SYMBOL_GPL(debug_check_no_locks_held); + +#ifdef __KERNEL__ +void debug_show_all_locks(void) +{ + struct task_struct *g, *p; + + if (unlikely(!debug_locks)) { + pr_warn("INFO: lockdep is turned off.\n"); + return; + } + pr_warn("\nShowing all locks held in the system:\n"); + + rcu_read_lock(); + for_each_process_thread(g, p) { + if (!p->lockdep_depth) + continue; + lockdep_print_held_locks(p); + touch_nmi_watchdog(); + touch_all_softlockup_watchdogs(); + } + rcu_read_unlock(); + + pr_warn("\n"); + pr_warn("=============================================\n\n"); +} +EXPORT_SYMBOL_GPL(debug_show_all_locks); +#endif + +/* + * Careful: only use this function if you are sure that + * the task cannot run in parallel! + */ +void debug_show_held_locks(struct task_struct *task) +{ + if (unlikely(!debug_locks)) { + printk("INFO: lockdep is turned off.\n"); + return; + } + lockdep_print_held_locks(task); +} +EXPORT_SYMBOL_GPL(debug_show_held_locks); + +asmlinkage __visible void lockdep_sys_exit(void) +{ + struct task_struct *curr = current; + + if (unlikely(curr->lockdep_depth)) { + if (!debug_locks_off()) + return; + pr_warn("\n"); + pr_warn("================================================\n"); + pr_warn("WARNING: lock held when returning to user space!\n"); + print_kernel_ident(); + pr_warn("------------------------------------------------\n"); + pr_warn("%s/%d is leaving the kernel with locks still held!\n", + curr->comm, curr->pid); + lockdep_print_held_locks(curr); + } + + /* + * The lock history for each syscall should be independent. So wipe the + * slate clean on return to userspace. + */ + lockdep_invariant_state(false); +} + +void lockdep_rcu_suspicious(const char *file, const int line, const char *s) +{ + struct task_struct *curr = current; + int dl = READ_ONCE(debug_locks); + bool rcu = warn_rcu_enter(); + + /* Note: the following can be executed concurrently, so be careful. */ + pr_warn("\n"); + pr_warn("=============================\n"); + pr_warn("WARNING: suspicious RCU usage\n"); + print_kernel_ident(); + pr_warn("-----------------------------\n"); + pr_warn("%s:%d %s!\n", file, line, s); + pr_warn("\nother info that might help us debug this:\n\n"); + pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s", + !rcu_lockdep_current_cpu_online() + ? "RCU used illegally from offline CPU!\n" + : "", + rcu_scheduler_active, dl, + dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n"); + + /* + * If a CPU is in the RCU-free window in idle (ie: in the section + * between ct_idle_enter() and ct_idle_exit(), then RCU + * considers that CPU to be in an "extended quiescent state", + * which means that RCU will be completely ignoring that CPU. + * Therefore, rcu_read_lock() and friends have absolutely no + * effect on a CPU running in that state. In other words, even if + * such an RCU-idle CPU has called rcu_read_lock(), RCU might well + * delete data structures out from under it. RCU really has no + * choice here: we need to keep an RCU-free window in idle where + * the CPU may possibly enter into low power mode. This way we can + * notice an extended quiescent state to other CPUs that started a grace + * period. Otherwise we would delay any grace period as long as we run + * in the idle task. + * + * So complain bitterly if someone does call rcu_read_lock(), + * rcu_read_lock_bh() and so on from extended quiescent states. + */ + if (!rcu_is_watching()) + pr_warn("RCU used illegally from extended quiescent state!\n"); + + lockdep_print_held_locks(curr); + pr_warn("\nstack backtrace:\n"); + dump_stack(); + warn_rcu_exit(rcu); +} +EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); |